Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
  • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
  • C07D307/26—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member
  • C07D307/28—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D407/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00
  • C07D407/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00 containing two hetero rings
  • C07D407/06—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00 containing two hetero rings linked by a carbon chain containing only aliphatic carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D407/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00
  • C07D407/14—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00 containing three or more hetero rings
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D493/00—Heterocyclic compounds containing oxygen atoms as the only ring hetero atoms in the condensed system
  • C07D493/12—Heterocyclic compounds containing oxygen atoms as the only ring hetero atoms in the condensed system in which the condensed system contains three hetero rings
  • C07D493/14—Ortho-condensed systems
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D493/00—Heterocyclic compounds containing oxygen atoms as the only ring hetero atoms in the condensed system
  • C07D493/22—Heterocyclic compounds containing oxygen atoms as the only ring hetero atoms in the condensed system in which the condensed system contains four or more hetero rings
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
  • C07F7/1804—Compounds having Si-O-C linkages
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
  • C07F9/6558—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom containing at least two different or differently substituted hetero rings neither condensed among themselves nor condensed with a common carbocyclic ring or ring system
  • C07F9/65586—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom containing at least two different or differently substituted hetero rings neither condensed among themselves nor condensed with a common carbocyclic ring or ring system at least one of the hetero rings does not contain nitrogen as ring hetero atom
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
  • C07F9/6561—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom containing systems of two or more relevant hetero rings condensed among themselves or condensed with a common carbocyclic ring or ring system, with or without other non-condensed hetero rings

Definitions

• Halichondrin B is a potent anticancer agent originally isolated from the marine sponge Halichondria okadai, and subsequently found in Axinella sp., Phakellia carteri, and Lissodendoryx sp. A total synthesis of halichondrin B was published in 1 992 (Aicher, T. D. et al., J. Am . Chem . Soc. 1 14:31 62-3164).
• Eribulin mesylate also called Halaven®, E7389, and the mesylate salt of B1 939
• a nontaxane microtubule dynamics inhibitor is a structurally simplified, synthetic analogue of halichondrin B. Methods and intermediates for the synthesis of eribulin mesylate and other halichondrin B analogues are described in International Publication Nos. WO 2005/1 18565, WO 2009/046308, WO 2009/064029, and WO 2009/124237; U.S. Patent No. 6,214,865; Austad et al., Synlett 24(3) :333-337, 2013; Austad et al., Synlett.
• the present invention provides methods for macrocyclization of intermediates in the synthesis of eribulin or a pharmaceutically acceptable salt thereof (e.g., eribulin mesylate).
• the invention also provides intermediates that can be employed in the macrocyclization reactions described herein.
• the invention provides a method of preparing an intermediate in the synthesis of eribulin, the method including performing a macrocyclization reaction on a non-macrocyclic intermediate, the macrocyclization reaction producing the intermediate in the synthesis of eribulin by forming a C.15-C.16, C.2-C.3, C.3-C.4, C.19-C.20, C.0-C.1 , or C.26-C.27 bond in the structure of eribulin.
• performing the macrocyclization reaction can involve contacting the non-macrocyclic intermediate (e.g., a compound of formula (IA)) with an olefin metathesis catalyst (e.g., a ruthenium-carbene complex).
• the non-macrocyclic intermediate can be a compound of formula (IA) or a salt thereof:
• R 2 is H or a hydroxyl protecting group
• R 3 is Ci -6 alkyl ether
• R 4 is H ;
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond ; or
• R 5 is H or a hydroxyl protecting group, and R 6 and R 7 combine to form a double bond ; or
• R 8 is H , and P 4 is H or a hydroxyl protecting group
• each P 3 is independently H or a hydroxyl protecting group
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an am inal or 1 ,3-oxazolidin-2-one-5-yl ;
• each P 3 and P 4 can be independently a hydroxyl protecting group (e.g., a silyl) .
• Pi can be a hydroxyl protecting group (e.g. , a silyl) .
• X can be 0.
• P 2 is a hydroxyl protecting group (e.g., a silyl).
• X can be N, and and P 2 , together with the atoms to which each is attached, can combine to form an aminal.
• R 2 and R 3 can combine to form a bond, and R 4 can be H.
• R 5 and R 6 can combine to form a bond, and R 7 can be H.
• R 8 can be H, and P 4 can be a hydroxyl protecting group (e.g., a silyl).
• performing the macrocyclization reaction involves reacting the non-macrocyclic intermediate (e.g., a compound of formula (IIA)) with an organic base (e.g., an organic base having a pKa of 11 ⁇ 2 (e.g., DBU or trialkylamine (e.g., triethylamine))) and a Lewis acid (e.g., a salt of Li, Mg, or Zn (e.g., lithium chloride or zinc trifluoromethanesulfonate)).
• the method can involve performing a Horner-Wadsworth-Emmons reaction on the compound of formula (IIA) to afford the compound of formula (IIB).
• the non-macrocyclic intermediate can be a compound of formula (IIA) or a salt thereof:
• each R is independently optionally substituted alkyl or optionally substituted aryl
• Ri is H or a hydroxyl protecting group, and R 2 and R 3 combine to form a double bond; or
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal;
• P 4 is H or a hydroxyl protecting group
• each of and P 2 is independently H or a hydroxyl protecting group, or
• X is N
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• each R can be optionally substituted alkyl.
• P 2 can be a hydroxyl protecting group (e.g., a silyl).
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• P ⁇ and R 2 can form a bond, and R 3 can be H.
• P 4 can be a hydroxyl protecting group (e.g., a silyl).
• performing the macrocyclization reaction involves contacting the non-macrocyclic intermediate (e.g., a compound of formula (IIIA)) with an olefin metathesis catalyst (e.g., a ruthenium-carbene complex).
• the non-macrocyclic intermediate can be a compound of formula (IIIA) or a salt thereof:
• Ri is H or a hydroxyl protecting group, and R 2 and R 3 combine to form a double bond; or
• X 3 is oxo, or X 3 combine with the carbon atom to which it is attached to form a ketal, a thioketal, or -(CH(OP 5 ))-, where P 5 is H or a hydroxyl protecting group; each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal;
• P 4 is H or a hydroxyl protecting group
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• X is N
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl;
• P 4 can be a hydroxyl protecting group (e.g., a silyl).
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• R 2 can form a bond, and R 3 can be H.
• X 3 can combine with the carbon atom to which it is attached to form -(CH(OP 5 ))-.
• P 5 can be H.
• P ⁇ can be a hydroxyl protecting group (e.g., silyl).
• P 2 can be a hydroxyl protecting group.
• performing the macrocyclization reaction includes contacting the non-macrocyclic intermediate (e.g., a compound of formula (IVA)) with a Cr(ll) salt and a Ni(ll) salt.
• the method can involve subjecting a compound of formula (IVA) to Nozaki-Hiyama-Kishi reaction conditions.
• the non-macrocyclic intermediate can be a compound of formula (IVA) or a salt thereof:
• Y is iodide, brom ide, or trifluoromethanesulfonate
• a can designate R stereogenic center, and Z is a sulfonate, chloride, brom ide, or iodide; or a can designate S stereogenic center, and Z is OR1 , where P is a hydroxyl protecting group;
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond ; or
• R 2 and R 3 combine to form a bond, and R 4 is H ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl ;
• a designates R stereogenic center
• b designates S stereogenic center
• Z is a sulfonate, chloride, bromide, or iodide
• a designates S stereogenic center
• b designates ft stereogenic center
• Z is OR ⁇ where is a hydroxyl protecting group
• Y can be bromide.
• R 2 and R 3 can combine to form a bond, and R 4 can be H.
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• formula (IVA) or (IVB) can be a hydroxyl protecting group (e.g., a silyl).
• P 2 can be a hydroxyl protecting group (e.g., a silyl).
• Z can be a sulfonate.
• Z can be OR where Ri can be a hydroxyl protecting group (e.g., Z can be an ester, carbonate, or carbamate (e.g., Z can be an ester)).
• performing the macrocyclization reaction involves contacting the non-macrocyclic intermediate (e.g., a compound of formula (VA)) with a base (e.g., a tertiary C 4 . 6 alkoxide (e.g., an alkali tertiary C 4 . 6 alkoxide)).
• a base e.g., a tertiary C 4 . 6 alkoxide (e.g., an alkali tertiary C 4 . 6 alkoxide)
• the method can involve subjecting a compound of formula (VA) to the Dieckmann reaction conditions.
• the non-macrocyclic intermediate can be a compound of formula (VA)
• Y is SO2P or COOP , where, when Y is SO2P , P is optionally substituted aryl or optionally substituted non-enolizable alkyl, and when Y is COOPM , P is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyi ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo, or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• R 2 is optionally substituted alkyl, optionally substituted arylalkyi, or optionally substituted aryl ;
• each of P ⁇ and P 2 is independently a hydroxyl protecting group
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl ;
• R 3 is H
• R 4 is optionally substituted Ci -6 alkyl ether
• R 5 is H ;
• R 5 is H , and R 3 and R 4 combine to form a double bond ;
• R 3 is H , and R 4 and R 5 combine to form a bond.
• Y can be S0 2 Ri (e.g. , can be optionally substituted aryl) .
• both P 3 groups and X 2 together with the atoms to which each is attached , can combine to form ketal.
• R 2 can be optionally substituted alkyl (e.g., unsubstituted Ci -6 alkyl) .
• R 3 can be H , and R 4 and R 5 can combine to form a bond.
• performing the macrocyclization reaction includes contacting the non-macrocyclic intermediate (e.g.
• a compound of formula (VIA)) with a Cr(l l) salt and a Ni(l l) salt can involve subjecting a compound of formula (VIA) to Nozaki-Hiyama-Kishi reaction conditions.
• the non-macrocyclic intermediate can be a compound of formula (VIA) or a salt thereof:
• Y is iodide, brom ide, or trifluoromethanesulfonate
• R 3 is H or a hydroxyl protecting group
• R 4 and R 5 combine to form a double bond
• each P 3 is independently H or a hydroxyl protecting group
• X 2 together with the carbon to which it is attached, form a carbonyl or -(CH(OR 6 ))-, where R 6 is H or a hydroxyl protecting group;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 , together with the carbon to which it is attached, form a carbonyl or -(CH(OR 6 ))-;
• (b1 ) Z is chloride, bromide, or iodide, and R ⁇ and R 2 combine to form a bond ;
• each of and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• P 4 is H or a hydroxyl protecting group.
• Z can be iodide, and R- ⁇ and R 2 can combine to form a bond.
• Y can be trifluoromethanesulfonate.
• R ⁇ can be H, or 0 and R ⁇ can combine to form a sulfonate.
• formula (VIA) or (VIB) can be a hydroxyl protecting group (e.g., a silyl).
• P 2 can be a hydroxyl protecting group (e.g., a silyl).
• R 3 can be H or a hydroxyl protecting group
• R 4 and R 5 can combine to form a double bond
• each P 3 can be independently H or a hydroxyl protecting group
• X 2 together with the carbon to which it is attached, can form a carbonyl or -(CH(OR 6 ))-, where R 6 can be H or a hydroxyl protecting group.
• R 3 can be a hydroxyl protecting group (e.g., a silyl), R 4 and R 5 can combine to form a double bond, each P 3 can be independently a hydroxyl protecting group, and X 2 , together with the carbon to which it is attached, can form a carbonyl or -(CH(OR 6 ))-, where R 6 can be H or a hydroxyl protecting group (e.g., 0 can combine with R 6 to form an ester).
• P 4 can be a hydroxyl protecting group (e.g., 0 and P 4 can combine to form an ester).
• Preparation of the compound of formula (VIB) from the compound of formula (VIA) can further involve
• the invention provides a method of preparing:
• the method involves:
• R 2 is H or a hydroxyl protecting group, R 3 is C 1 -6 alkyl ether, and R 4 is H ;
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond ; or
• R 5 is H or a hydroxyl protecting group, and R 6 and R 7 combine to form a double bond ; or
• R 8 is H , and P 4 is H or a hydroxyl protecting group
• each P 3 is independently H or a hydroxyl protecting group
• each of ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl ;
• the method can involve (B) producing a compound of formula (IC) from the compound of formula (IB), the compound of formula (IC) having the following structure:
• the method can involve (C) producing a compound of formula (ID) from the compound of formula (IC), the compound of formula (ID) having the following structure:
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal; and each of the remaining variables is as defined for formula (IC).
• the method can further involve (D) producing eribulin or eribulin mesylate from the compound of formula (ID).
• P 4 can be a hydroxyl protecting group (e.g., a silyl) .
• R 2 and R 3 can combine to form a bond, and R 4 can be H.
• R 5 and R 6 can combine to form a bond, and R 7 can be H.
• R 8 can be H, and P 4 can be a hydroxyl protecting group (e.g., a silyl).
• each P 3 can be independently a hydroxyl protecting group (e.g., a silyl) .
• P 3 can be H or a hydroxyl protecting group (e.g., a silyl).
• P ⁇ can be a hydroxyl protecting group (e.g., a silyl) .
• X can be 0.
• P 2 is a hydroxyl protecting group (e.g., a silyl).
• X can be N, and P ⁇ and P 2 , together with the atoms to which each is attached, can combine to form an aminal.
• the method can further involve oxidizing the compound of formula (IB) (e.g., when R 8 is H) with an olefin metathesis catalyst, e.g., by reacting with an oxidizing agent capable of oxidizing an alcohol to a carbonyl group (e.g., Dess-Martin periodinane).
• an oxidizing agent capable of oxidizing an alcohol to a carbonyl group e.g., Dess-Martin periodinane.
• P 4 is a hydroxyl protecting group (e.g., a silyl) in the compound of formula (IB)
• this compound can be reacted with a hydroxyl protecting group removing agent prior to oxidizing the compound of formula (IB).
• Producing the compound of formula (IB) from the compound of formula (IA) can involve reacting the compound of formula (IA) with an olefin metathesis catalyst.
• Producing the compound of formula (IC) can include oxidizing the compound of formula (IB), where, in the compound of formula (IB), R 8 is H, and P 4 is H, e.g., by reacting the compound of formula (IB) with an oxidizing agent capable of oxidizing an alcohol to a carbonyl group (e.g., Dess-Martin periodinane).
• an oxidizing agent capable of oxidizing an alcohol to a carbonyl group e.g., Dess-Martin periodinane
• Producing the compound of formula (ID) can include reacting the compound of formula (IC) with a 1 ,4- reducing agent.
• the compound of formula (ID), in which each P 3 is independently a hydroxyl protecting group, can be reacted with a hydroxyl protecting group removing agent to afford tej compound of formula
• each P 3 is H or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal.
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• P ⁇ can be H.
• X can be 0, and P 2 can be H.
• Producing eribulin or eribulin mesylate from the compound of formula (ID) can include aminating the compound of formula (ID).
• X and P 2 can combine to form a masked amino.
• Producing eribulin or eribulin mesylate from the compound of formula (I D) can involve reacting the compound of form ula (ID) with an am ino unmasking agent. Eribulin mesylate can be produced by salifying eribulin with methanesulfonic acid .
• the method involves:
• each R is independently optionally substituted alkyl or optionally substituted aryl ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• P 4 is H or a hydroxyl protecting group
• each of ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl ;
• each R can be optionally substituted alkyl.
• P ⁇ can be a hydroxyl protecting group (e.g., a silyl).
• P 2 can be a hydroxyl protecting group (e.g., a silyl).
• ⁇ and R 2 can form a bond, and R 3 can be H.
• P 4 can be a hydroxyl protecting group (e.g., a silyl).
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• Producing the compound of formula (IIB) can involve reacting the compound of formula (IIA) with an organic base (e.g., an organic base having a pKa of 1 1 ⁇ 2 (e.g., DBU or trialkylamine (e.g.,
• Lewis acid e.g., a salt of Li, Mg, or Zn (e.g., lithium chloride or zinc
• Producing the compound of formula (ID) can involve reacting the compound of formula (I IB) with a hydroxyl protecting group removing agent.
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• X can be 0, and P 2 can be H.
• Producing eribulin or eribulin mesylate from the compound of formula (I D) can include am inating the compound of formula (ID) .
• X and P 2 can combine to form a masked amino.
• Producing eribulin or eribulin mesylate from the compound of formula (I D) can involve reacting the compound of form ula (ID) with an am ino unmasking agent.
• Eribulin mesylate can be produced by salifying eribulin with methanesulfonic acid .
• the method involves:
• X 3 is oxo, or X 3 combines with the carbon atom to which it is attached to form a ketal, a thioketal, or -(CH(OP 5 ))-, where P 5 is H or a hydroxyl protecting group; each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal ;
• P 4 is H or a hydroxyl protecting group
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• P 4 can be a hydroxyl protecting group (e.g., a silyl) .
• R 2 can form a bond
• R 3 can be H.
• X 3 can combine with the carbon atom to which it is attached to form -(CH(OP 5 ))-.
• P 5 can be H.
• formula (II IA) or (II IB) can be a hydroxyl protecting group (e.g., silyl).
• P 2 can be a hydroxyl protecting group.
• P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• Producing the compound of formula (II IB) can involve reacting the compound of formula (II IA) with an olefin metathesis catalyst.
• Producing the compound of formula (ID) can involve oxidizing (e.g., by reacting with an oxidizing agent capable of oxidizing an alcohol to a carbonyl group) the compound of formula (I IIB), where, in the compound of formula (I IIB), X 3 , together with the carbon to which it is attached, forms -(CH(OP 5 ))-, where P 5 is H.
• Producing the compound of formula (ID) can also involve reacting the compound of formula (I IIB), where, in the compound of formula (II IB), P 4 is a hydroxyl protecting group, and R 4 and R 5 combine to form a double bond, with a hydroxyl protecting group removing agent.
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• X can be 0, and P 2 can be H.
• Producing eribulin or eribulin mesylate from the compound of formula (ID) can include aminating the compound of formula (ID).
• X and P 2 can combine to form a masked amino.
• Producing eribulin or eribulin mesylate from the compound of formula (ID) can involve reacting the compound of formula (ID) with an amino unmasking agent.
• Eribulin mesylate can be produced by salifying eribulin with methanesulfonic acid.
• the method includes:
• Y is iodide, bromide, or trifluoromethanesulfonate
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond; or
• R 2 and R 3 combine to form a bond, and R 4 is H ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal; and
• X is 0, and each of and P 2 is independently H or a hydroxyl protecting group
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl ;
• a designates R stereogenic center
• b designates S stereogenic center
• Z is a sulfonate, chloride, brom ide, or iodide
• a designates S stereogenic center
• b designates ft stereogenic center
• Z is ORi , where is a hydroxyl protecting group
• Y can be bromide.
• R 2 and R 3 can combine to form a bond, and R 4 can be H.
• Pi can be a hydroxyl protecting group (e.g., a silyl) .
• P 2 can be a hydroxyl protecting group (e.g., a silyl).
• Z can be a sulfonate.
• Z can be OR where R ⁇ can be a hydroxyl protecting group (e.g., Z can be an ester, carbonate, or carbamate (e.g., Z can be an ester)).
• R ⁇ can be a hydroxyl protecting group
• Z can be an ester, carbonate, or carbamate (e.g., Z can be an ester)
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• Producing the compound of formula (IVB) can involve reacting the compound of formula (IVA) with a Cr(l l) salt and a Ni(ll) salt.
• Producing the compound of formula (IVB) can involve subjecting the compound of formula (IVA) to Nozaki-Hiyama-Kishi reaction conditions.
• Producing the compound of formula (ID) can involve the step of nucleophilic ring-closing of the compound of formula (IVB).
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• X can be 0, and P 2 can be H.
• Producing eribulin or eribulin mesylate from the compound of formula (ID) can include aminating the compound of formula (ID).
• X and P 2 can combine to form a masked amino.
• Producing eribulin or eribulin mesylate from the compound of formula (ID) can involve reacting the compound of formula (ID) with an amino unmasking agent.
• Eribulin mesylate can be produced by salifying eribulin with methanesulfonic acid.
• the method includes:
• Y is SO2P or COOP , where, when Y is SO2P , P is optionally substituted aryl or optionally substituted non-enolizable alkyl, and when Y is COOPM , P is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyi ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo, or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• R 2 is optionally substituted alkyl, optionally substituted arylalkyi, or optionally substituted aryl ;
• each of P ⁇ and P 2 is independently a hydroxyl protecting group
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl ;
• R 3 is H , R 4 is ether, and R 5 is H ;
• R 5 is H , and R 3 and R 4 , together with the bond connecting the atoms to which each is attached, combine to form a double bond ;
• R 3 is H , and R 4 and R 5 combine to form a bond ;
• Y can be S0 2 Ri (e.g., P can be optionally substituted aryl).
• R 2 can be optionally substituted alkyl (e.g., unsubstituted Ci -6 alkyl).
• R 3 can be H, and R 4 and R 5 can combine to form a bond.
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• Producing the compound of formula (VB) can involve reacting the compound of formula (VA) with a strong base (e.g., a tertiary C 4 . 6 alkoxide).
• a strong base e.g., a tertiary C 4 . 6 alkoxide
• Producing the compound of formula (ID) can involve reacting the compound of formula (VB), in which Y is S0 2 Ri , and RT is optionally substituted aryl, with an electron-transferring reducing agent (e.g., Sm l 2 , Mg(0), or Cr(l ll) with Mn(0)).
• an electron-transferring reducing agent e.g., Sm l 2 , Mg(0), or Cr(l ll) with Mn(0).
• both P 3 groups and X 2 together with the atoms to which each is attached, can combine to form ketal.
• X can be 0, and P 2 can be H.
• Producing eribulin or eribulin mesylate from the compound of formula (ID) can include aminating the compound of formula (ID).
• X and P 2 can combine to form a masked amino.
• Producing eribulin or eribulin mesylate from the compound of formula (ID) can involve reacting the compound of formula (ID) with an amino unmasking agent.
• Eribulin mesylate can be produced by salifying eribulin with methanesulfonic acid.
• the method includes:
• Y is iodide, brom ide, or trifluoromethanesulfonate
• R 3 is H or a hydroxyl protecting group
• R 4 and R 5 combine to form a double bond
• each P 3 is independently H or a hydroxyl protecting group
• X 2 together with the carbon to which it is attached, forms a carbonyl or -(CH(OR 6 ))-, where R 6 is H or a hydroxyl protecting group;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 , together with the carbon to which it is attached, forms a carbonyl or -(CH(OR 6 ))-;
• (b1 ) Z is chloride, bromide, or iodide, and and R 2 combine to form a bond ;
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl ;
• P 4 is H or a hydroxyl protecting group
• Producing the compound of formula (VIB) can include reacting the compound of formula (VIA) with a Cr(l l) salt and a Ni(ll) salt.
• Producing the compound of formula (ID) can include reacting the compound of formula (VI B) with a hydroxyl protecting group removing agent.
• both P 3 groups and X 2 together with the atoms to which each is attached , can combine to form ketal.
• X can be 0, and P 2 can be H .
• Producing eribulin or eribulin mesylate from the compound of form ula (I D) can include am inating the compound of formula (ID) .
• X and P 2 can combine to form a masked amino.
• Producing eribulin or eribulin mesylate from the compound of formula (I D) can involve reacting the compound of form ula (ID) with an am ino unmasking agent.
• Eribulin mesylate can be produced by salifying eribulin with methanesulfonic acid .
• the invention provides a method of preparing an intermediate in the synthesis of eribulin, the method including perform ing a Prins reaction by contacting a compound of form ula (VI IA) with a compound of form ula (VI I B) and R 3 OH ,
• R 3 can be an optionally substituted acyl
• Yi is S0 2 Ri or COOP , and P is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl ;
• XT is 0, or X together with the carbon to which it is attached, forms a cyclic acetal ;
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• P 3 is H or a hydroxyl protecting group
• each P 4 is independently a hydroxyl protecting group, or both P 4 groups, together with the atoms to which each is attached, combine to form a cyclic protected diol
• Performing a Prins reaction can involve reacting the compound of formula (VIIA) with a Lewis acid boron trifluoride or a solvate thereof).
• the invention provides a method of preparing an intermediate in the synthesis of eribulin, the method can involve:
• each of P 2 , and P 4 can be independently a hydroxyl protecting group, or Pi and P 4 , together with the atoms to which each can be attached, can combine to form a cyclic protected diol;
• R 2 can be H or -CH 2 CH 2 OP 5 , and P 5 can be a hydroxyl protecting group
• VI IID (VI IID) ;
• Y can be optionally substituted C ⁇ e alkyl ether
• R 2 can be -CH 2 CH 2 OP 5
• X 2 can be oxo, or X 2 , together with the carbon to which it can be attached, forms a ketal or -(CH(OP 6 ))-, where P 6 can be a hydroxyl protecting group.
• the method further includes:
• each R 4 is independently optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl; (I) reacting the compound of formula (VIIIJ) with a Lewis acid to afford a compound of formula
• the invention provides compounds of formulas (IA), (IB), (IC), (IIA), (IIB), (IIIA), (IIIB), (IVA), (IVB), (IVE), (VA), (VB), (VIA), (VIB), (VIIB), and (VIIC).
• the invention also provides compounds of formulas (VIIIC), (VIIID), (VIIIE), (VIIIF), (VIIIG), (VIIIH), (VIIIJ), (VIIIK), and (VIIIL).
• a compound of the fifth aspect can be a compound of formula (IA) or (IB):
• R 2 is H or a hydroxyl protecting group, R 3 is C ⁇ e alkyl ether, and R 4 is H;
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond; or
• R 5 is H or a hydroxyl protecting group, and R 6 and R 7 combine to form a double bond ; or
• R 8 is H , and P 4 is H or a hydroxyl protecting group
• each P 3 is independently H or a hydroxyl protecting group
• X is O
• each of ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an am inal or 1 ,3-oxazolidin-2-one-5-yl.
• a compound of the fifth aspect can be a compound of form ula (IC) :
• each P 3 is independently a hydroxyl protecting group
• X is 0, Pi is a hydroxyl protecting group, and P 2 is H or a hydroxyl protecting group; or
• a compound of fifth aspect can be a compound of formula (I I A) or (M B) :
• each R is independently optionally substituted alkyl or optionally substituted aryl ;
• Ri is H or a hydroxyl protecting group, and R 2 and R 3 combine to form a double bond ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• P 4 is H or a hydroxyl protecting group
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• a compound of the fifth aspect can be a compound of form ula (I I IA) or (N I B) :
• X 3 is oxo, or X 3 combines with the carbon atom to which it is attached to form a ketal, a thioketal, or -(CH(OP 5 ))-, where P 5 is H or a hydroxyl protecting group;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• P 4 is H or a hydroxyl protecting group
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• a compound of the fifth aspect can be a compound of form ula (IVA) or (IVB) :
• Y is iodide, brom ide, or trifluoromethanesulfonate
• (a1 ) a designates R stereogenic center
• b designates S stereogenic center
• Z is a
• (a2) a designates S stereogenic center, b designates R stereogenic center, and Z is OP , where P is a hydroxyl protecting group;
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond ; or
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• each of ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl
• a compound of the fifth aspect can be a compound of form ula (VA) or (VB) :
• Y is SO2P or COOP , where, when Y is SO2P , P is optionally substituted aryl or optionally substituted non-enolizable alkyl, and when Y is COOPM , RI is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyi ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo, or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• R 2 is optionally substituted alkyl, optionally substituted arylalkyi, or optionally substituted aryl ;
• each of ⁇ and P 2 is independently a hydroxyl protecting group
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• Y is iodide, brom ide, or trifluoromethanesulfonate
• P 4 is H or a hydroxyl protecting group
• R 3 is H or a hydroxyl protecting group
• R 4 and R 5 combine to form a double bond
• each P 3 is independently H or a hydroxyl protecting group
• X 2 together with the carbon to which it is attached, forms a carbonyl or -(CH(OR 6 ))-, where R 6 is H or a hydroxyl protecting group;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 , together with the carbon to which it is attached, forms a carbonyl or -(CH(OR 6 ))-;
• (b1 ) Z is chloride, bromide, or iodide, and and R 2 combine to form a bond ;
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• a compound of the fifth aspect can be a compound of form ula (VI IC) :
• Yi is S0 2 Ri or COOR1 , and P is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl ;
• P 3 is H or a hydroxyl protecting group
• each P 4 is independently a hydroxyl protecting group, or both P 4 groups, together with the atoms to which each is attached, combine to form a cyclic protected diol
• R 3 is an optionally substituted acyl
• each of Pi and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• a compound of the fifth aspect can be a compound of form ula (VI I B) :
• P 3 is a hydroxyl protecting group
• each P 4 is independently a hydroxyl protecting group, or both P 4 groups, together with the atoms to which each is attached, combine to form a cyclic protected diol
• R 4 is is H or where X 2 is 0, -CH 2 -, or NP 5 , where P 5 is sulfonyl.
• a compound of the fifth aspect can be a compound of formula (IVE) :
• Y is iodide, bromide, or trifluoromethanesulfonate
• Z is an ester, a sulfonate, chloride, bromide, or iodide
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal; and
• R 2 is H or a hydroxyl protecting group, R 3 and R 4 combine to form a double bond;
• R 7 is H or a hydroxyl protecting group, and R 8 and R 9 combine to form a double bond;
• X 3 is oxo and R 10 is H or -OP 5 , where P 5 is H or an ether hydroxyl protecting group; or
• Compounds useful in the invention may be isotopically labeled compounds.
• Useful isotopes include hydrogen, carbon, nitrogen, and oxygen (e.g., 2 H, 3 H, 13 C, 14 C, 15 N, 18 0, and 17 0).
• Isotopically-labeled compounds can be prepared by synthesizing a compound using a readily available isotopically-labeled reagent in place of a non-isotopically-labeled reagent.
• a number following an atomic symbol indicates that total number of atoms of that element that are present in a particular chemical moiety.
• other atoms such as hydrogen atoms, or substituent groups, as described herein, may be present, as necessary, to satisfy the valences of the atoms.
• an unsubstituted C 2 alkyl group has the formula -CH 2 CH 3 .
• a reference to the number of carbon atoms includes the divalent carbon in acetal and ketal groups but does not include the carbonyl carbon in acyl, ester, carbonate, or carbamate groups.
• a reference to the number of oxygen, nitrogen, or sulfur atoms in a heteroaryl group only includes those atoms that form a part of a heterocyclic ring.
• acetal is meant -0-(CHR)-0- where R is H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyi.
• acyl is meant -C(0)R, where R is H, alkyl, alkenyl, aryl, or arylalkyi. In exemplary acyl groups, R is H, C 1-12 alkyl (e.g., C 1 -8 , C 1 -6 , C 1-4 , C 2 .
• C 2 . 12 alkenyl e.g., C 2 . 8 , C 2 . 6 , C 2 . 4 , C 3 -i 2 , or C 3 - 6 alkenyl
• C 6 . 20 aryl e.g., C 6 . 15 , C 6 . 10 , C 8 - 20 , or C 8 -i 5 aryl
• monocyclic C 1 -6 heteroaryl e.g., monocyclic C 1 -4 or C 2 .
• any heteroaryl group present in an acyl group has from 1 to 4 heteroatoms selected independently from 0, N, and S.
• An acyl group can be unsubstituted or substituted (e.g., optionally substituted acyl).
• the substituent R is H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyi.
• acylating agent is meant a compound that reacts with an amine or a hydroxyl group to produce an amide or an ester, respectively.
• An acylating agent has a formula R-LG, where R is acyl, and LG is halogen, carbonate, or -OR', where R' is acyl.
• alkoxide is meant an anionic compound RO " , where R is alkyl.
• a counterion for alkoxide can be an alkali metal cation, an alkali earth metal cation, or a tetraalkylammonium cation.
• Alkoxide can be optionally substituted in the same manner as alkyl.
• alkoxy is meant -OR, where R is alkyl. Alkoxy can be optionally substituted in the same manner as alkyl.
• alkoxyalkyl is meant -OR, where R is alkyl substituted by alkoxy. Each portion of the alkoxyalkyl can be optionally substituted in the same manner as alkyl.
• alkyl is meant a straight or branched chain saturated cyclic (i.e., cycloalkyl) or acyclic hydrocarbon group of from 1 to 12 carbons, unless otherwise specified.
• exemplary alkyl groups include C 1-8 , C 1 -6 , C 1-4 , C 2 _7 , C 3 . 12 , and C 3 . 6 alkyl. Specific examples include methyl, ethyl, 1 -propyl, 2-propyl, 2-methyl-1 -propyl, 1 -butyl, 2-butyl, and the like.
• Alkyl group can be optionally substituted with 1 , 2, 3, or 4 substituents selected from the group consisting of halogen, alkoxy, aryloxy, arylalkyloxy, oxo, alkylthio, alkylenedithio, alkylamino, [alkenyljalkylamino, [aryljalkylamino, [arylalkyljalkylamino, dialkylamino, silyl, sulfonyl, cyano, nitro, carboxyl, and azido.
• substituents selected from the group consisting of halogen, alkoxy, aryloxy, arylalkyloxy, oxo, alkylthio, alkylenedithio, alkylamino, [alkenyljalkylamino, [aryljalkylamino, [arylalkyljalkylamino, dialkylamino, silyl, sulfonyl,
• alkylamino is meant -NHR, where R is alkyl.
• alkenyljalkylamino is meant -NRR', where R is alkyl, and R' is alkenyl.
• aryljalkylamino is meant -NRR', where R is alkyl, and R' is aryl.
• [arylalkyljalkylamino” is meant -NRR', where R is alkyl, and R' is arylalkyi.
• dialkylamino is meant - NR 2 , where each R is alkyl, selected independently.
• alkylene is meant a divalent alkyl group. Alkylene groups can be optionally substituted in the same manner as alkyl groups. For example, a Ci alkylene group is -CH 2 -.
• alkylenedithio is meant -S-alkylene-S-.
• Alkylenedithio can be optionally substituted in the same manner as an alkylene group.
• alkylthio is meant -SR, where R is alkyl. Alkylthio can be optionally substituted in the same manner as an alkyl group.
• alkenyl is meant a straight or branched chain cyclic or acyclic hydrocarbon group of, unless otherwise specified, from 2 to 12 carbons and containing one or more carbon-carbon double bonds. Exemplary alkenyl groups include C 2 . 8 , C 2 . 7 , C 2 . 6 , C 2 . 4 , C 3 -i 2 , and C 3 - 6 alkenyl.
• Alkenyl group can be optionally substituted in the same manner as alkyl groups.
• Alkenyl groups, used in any context herein, may also be substituted with an aryl group.
• amido is meant -NHR, where R is acyl. Amido can be optionally substituted in the same manner as acyl.
• aminal is meant -0-CR 2 -NR'-, where each R is independently H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyl, or both R groups are together optionally substituted alkylene, and R' is H or an /V-protecting group. In particular, R' can be an /V-protecting group (e.g., Boc).
• amino is meant -NR 2 , where N and R 2 combine to form azido, or each R is independently H or an N- protecting group, or both R combine to form an /V-protecting group. Amino can be unmasked, when each R is H, or masked, when at least one R is not H. Thus, optionally masked amino can be masked or unmasked amino.
• aryl is meant a monocyclic or multicyclic ring system having one or more aromatic rings, where the ring system is carbocyclic or heterocyclic. Heterocyclic aryl groups are also referred to as heteroaryl groups. A heteroaryl group includes 1 to 4 atoms selected independently from 0, N, and S.
• Exemplary carbocyclic aryl groups include C 6 - 20 , C 6 -i 5 , C 6 -io, C 8 - 20 , and C 8 -i 5 aryl.
• a preferred aryl group is a C6-1 0 aryl group.
• Specific examples of carbocyclic aryl groups include phenyl, indanyl, indenyl, naphthyl, phenanthryl, anthracyl, and fluorenyl.
• Exemplary heteroaryl groups include monocylic rings having from 1 to 4 heteroatoms selected independently from 0, N, and S and from 1 to 6 carbons (e.g., C 1 -6 , C 1 -4 , and C 2 . 6 ).
• Monocyclic heteroaryl groups preferably include from 5 to 9 ring members.
• Other heteroaryl groups preferably include from 4 to 19 carbon atoms (e.g., C 4-10 ).
• Specific examples of heteroaryl groups include pyridinyl, quinolinyl, dihydroquinolinyl, isoquinolinyl, quinazolinyl, dihydroquinazolyl, and tetrahydroquinazolyl.
• Aryl group can be optionally substituted with 1 , 2, 3, 4, or 5 substituents selected from the group consisting of alkyl, alkenyl, aryl, arylalkyl, halogen, alkoxy, aryloxy, arylalkyloxy, alkylthio, alkylenedithio, alkylamino, [alkenyljalkylamino, [aryljalkylamino, [arylalkyljalkylamino, dialkylamino, silyl, sulfonyl, cyano, nitro, carboxyl, and azido.
• arylalkyi is meant -R'R", where R' is alkylene, and R" is aryl.
• Arylalkyi can be optionally substituted in the same manner as defined for each R' and R" group.
• arylalkyloxy is meant -OR, where R is arylalkyi.
• Arylalkyloxy can be optionally substituted in the same manner as defined for arylalkyi.
• aryloxy is meant -OR, where R is aryl.
• Aryloxy can be optionally substituted in the same manner as aryl.
• boronate is meant -OBRO-, where R is alkyl, alkenyl, aryl, arylalkyi, alkoxy, or 2,6- diacetamidophenyl. Boronate can be substituted, when R is a substituted alkyl, substituted alkenyl, substituted aryl, substituted arylalkyi, or substituted alkoxy.
• boronate can be unsubstituted, when R is unsubstituted alkyl, unsubstituted alkenyl, aryl, unsubstituted arylalkyi, unsubstituted alkoxy, or 2,6-diacetamidophenyl.
• carboxylate is meant a group, when a hydroxyl protecting group, having the formula -OC(0)NR 2 , or, when an amine protecting group, having the formula -NR'-C(0)OR, where each R and R' is
• carbonate is meant -OC(0)OR, where R is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyi.
• carbonyl is meant -C(O)-.
• Carboxyl is meant -C(0)OH, in free acid, ionized, or salt form.
• carboxylic acid is meant R-OH, where R is optionally substituted acyl.
• carboxylic acid anhydride is meant R-O-R, where each R is independently optionally substituted acyl.
• dicarbonyl is meant -C(0)-C(0)-.
• ester is meant -OC(0)R, where -C(0)R is an optionally substituted acyl group.
• ether is meant -OR, where R is alkyl, alkenyl, arylalkyl, silyl, or 2-tetrahydropyranyl. Ether can be optionally substituted as defined for each R group.
• halogen is meant fluoro, chloro, bromo, or iodo.
• hydroxyl protecting group is meant any group capable of protecting the oxygen atom to which it is attached from reacting or bonding. Hydroxyl protecting groups are known in the art, e.g., as described in Wuts, Greene's Protective Groups in Organic Synthesis, Wiley-lnterscience, 4th Edition, 2006.
• Exemplary protecting groups are independently selected from the group consisting of esters, carbonates, carbamates, sulfonates, and ethers.
• R of the acyl group is Ci _i 2 alkyl (e.g., Ci -8 , Ci -6 , Ci -4 , C 2 . 7 , C 3 . 12, and C 3 -6 alkyl), C2-12 alkenyl (e.g., C 2 . 8 , C 2 . 6 , C 2 . 4 , C3-12, and C 3 - 6 alkenyl), carbocyclic C 6 - 2 o aryl (e.g., C 6 .
• acyl groups for use in esters include formyl, benzoylformyl, acetyl (e.g.,
• any heteroaryl group present in an ester group has from 1 to 4 heteroatoms selected independently from O, N, and S.
• R is C 1 -1 2 alkyl (e.g., C 1 -8 , C 1 -6 , C 1 -4 , C 2 . 7 , C 3 _i 2 , and C 3 . 6 alkyl), C 2 _i 2 alkenyl (e.g., C 2 . 8 , C 2 . 6 , C 2 . 4 , C 3 .i 2 , and C 3 . 6 alkenyl), carbocyclic C 6 .
• aryl e.g., C 6 _i 5 , C 6 _i 0 , C 8 . 20 , and Ce-15 aryl
• monocyclic Ci -6 heteroaryl e.g., Ci -4 and C 2 . 6 heteroaryl
• C 4 _i 9 heteroaryl e.g., C 4 _i 0 heteroaryl
• any heteroaryl group present in a carbonate group has from 1 to 4 heteroatoms selected independently from 0, N, and S.
• each R is independently H, C 1-12 alkyl (e.g., Ci_ 8 , C 1 -6 , C 1 -4 , C 2 - 7 , C 3 _i 2 , and C 3 . 6 alkyl), C 2 -i 2 alkenyl (e.g., C 2 . 8 , C 2 - 6 , C 2 . 4 , C 3 _i 2 , and C 3 . 6 alkenyl), carbocyclic C 6 . 20 aryl (e.g., C 6 _i 5 , C 6 _i 0 , C 8 .
• C 1-12 alkyl e.g., Ci_ 8 , C 1 -6 , C 1 -4 , C 2 - 7 , C 3 _i 2 , and C 3 . 6 alkyl
• C 2 -i 2 alkenyl e.g., C 2 . 8 , C 2 - 6 , C 2 . 4 , C 3 _i
• C 8 _i 5 aryl monocyclic C 1 -6 heteroaryl (e.g., C 1 -4 and C 2 - 6 heteroaryl), C 4 _i 9 heteroaryl (e.g., C 4 _i 0 heteroaryl), (C 6 -i 5)aryl(Ci. 6 )alkyl, (C 4 .i 9 )heteroaryl(Ci. 6 )alkyl, or (Ci_ 6 )heteroaryl(Ci. 6 )alkyl.
• Specific examples include N-phenyl and N-methyl-N-(o-nitrophenyl) carbamates.
• any heteroaryl group present in a carbamate group has from 1 to 4 heteroatoms selected independently from 0, N, and S.
• Exemplary ether hydroxyl protecting groups include Ci _i 2 alkyl (e.g., Ci_ 8 , Ci _6, Ci_4, C 2 _7, C 3 _i 2 , and C 3 . 6 alkyl), C 2 _i 2 alkenyl (e.g., C 2 . 8 , C 2 . 6 , C 2 . 4 , C 3 _i 2 , and C 3 . 6 alkenyl), (C 6 _i 5 )aryl(Ci_ 6 )alkyl, (C 4 -i 9 )heteroaryl(Ci.
• alkylethers include methyl and t-butyl, and an example of an alkenyl ether is allyl.
• Ether hydroxyl protecting groups can be used to protect a carboxyl group (e.g., with a Ci_i 2 alkyl (e.g., Ci -8 , Ci -6 , Ci -4 , C 2 . 7 , C3-12, and C 3 - 6 alkyl), (C 6 -i 5)aryl(Ci -6 )alkyl, (Ci.6)alkoxy(Ci -6 )alkyl, (d_ 6 )alkylthio(C 1 . 6 )alkyl, or (C 6 -io)aryl(C 1 .6)alkoxy(C 1 . 6 )alkyl).
• a Ci_i 2 alkyl e.g., Ci -8 , Ci -6 , Ci -4 , C 2 . 7 , C3-12, and C 3 - 6 alkyl
• C 6 -i 5)aryl(Ci -6 )alkyl e.g., Ci -8
• alkoxyalkyls and alkylthioalkyls that can be used as ether hydroxyl protecting groups include methoxymethyl, methylthiomethyl, (2- methoxyethoxy)methyl, and ⁇ -( ⁇ 3 ⁇ ) ⁇ .
• arylalkyi groups that can be used as ether hydroxyl protecting groups include benzyl, p-methoxybenzyl (MPM), 3,4-dimethoxybenzyl, triphenylmethyl (trityl), o-nitrobenzyl, p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl, naphthylmethyl, and 2- and 4-picolyl ethers.
• silylethers include trimethylsilyl (TMS), triethylsilyl (TES), t-butyldimethylsilyl (TBS), t-butyldiphenylsilyl (TBDPS), triisopropylsilyl (TIPS), and triphenylsilyl (TPS) ethers.
• TMS trimethylsilyl
• TES triethylsilyl
• TBS t-butyldimethylsilyl
• TIPS triisopropylsilyl
• TPS triphenylsilyl
• TPS triphenylsilyl
• An example of an arylalkyloxyalkylether is benzyloxymethyl ether.
• any heteroaryl group present in an ether group has from 1 to 4 heteroatoms selected
• Vicinal or 1 ,3-diols may be protected with a diol protecting group (e.g., to produce a "cyclic protected diol"), such as acetal (e.g., containing Ci -6 alkylene) , ketal (e.g., containing C 3 _6 alkylene or C 3 . 6 cycloalkyl), cyclic silylene, cyclic carbonate, and cyclic boronate.
• a diol protecting group e.g., to produce a "cyclic protected diol”
• acetal e.g., containing Ci -6 alkylene
• ketal e.g., containing C 3 _6 alkylene or C 3 . 6 cycloalkyl
• cyclic silylene cyclic carbonate
• cyclic carbonate cyclic carbonate
• acetal and ketal groups include methylene-dioxo, ethylidene-dioxo, benzylidene-dioxo, isopropylidene-dioxo, cyclohexylidene-dioxo, and cyclopentylidene-dioxo.
• An example of a cyclic silylene is di-t-butylsilylene.
• Another diol protecting group is 1 ,1 ,3,3-tetraisopropylsiloxanediyl.
• cyclic boronates include methyl, ethyl, phenyl, and 2,6-diacetamidophenyl boronates.
• Protecting groups may be substituted as is known in the art; for example, aryl and arylalkyi groups, such as phenyl, benzyl, naphthyl, or pyridinyl, can be substituted with Ci -6 alkyl, Ci -6 alkoxy, nitro, cyano, carboxyl, or halogen.
• Alkyl groups such as methyl, ethyl, isopropyl, n-propyl, t-butyl, n-butyl, and sec-butyl, and alkenyl groups, such as vinyl and allyl, can also be substituted with oxo, arylsulfonyl, halogen, and trialkylsilyl groups.
• Preferred protecting groups are TBS and Piv.
• Protecting groups that are orthogonal are removed under different conditions, as in known in the art.
• imido is meant -NR 2 , where each R is independently optionally substituted acyl.
• ketal is meant -0-CR 2 -0- where each R is independently optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyi, or both R groups are together optionally substituted alkylene.
• macrocyclization is meant a reaction converting a non-macrocyclic compound into a compound containing at least one n-membered ring, where n is equal to or greater than 16.
• non-enolizable is meant a group that, either alone or in combination with a group to which it is attached, cannot form an enol through a deprotonation/reprotonation sequence.
• a “non- enolizable alkyl” can be bonded to a sulfone group or to a carbonyl group through a quaternary carbon atom (i.e., the carbon atom that is not bonded to a hydrogen atom).
• non-macrocyclic is meant a compound not containing rings or containing one or more m-membered rings, where m is less than or equal to 1 5.
• /V-protecting group is meant a group protecting a nitrogen atom in a molecule from participating in one or more undesirable reactions during chemical synthesis (e.g., oxidation reactions, or certain nucleophilic and electrophilic substitutions). Commonly used /V-protecting groups are disclosed in Wuts, Greene's Protective Groups in Organic Synthesis, Wiley-lnterscience, 4th Edition, 2006.
• N- protecting groups include acyl (e.g., formyl, acetyl, trifluoroacetyl, propionyl, pivaloyl, t-butylacetyl, 2- chloroacetyl, 2-bromoacetyl, trifluoroacetyl, trichloroacetyl, phthalyl, o-nitrophenoxyacetyl, a-chlorobutyryl, benzoyl, 4-chlorobenzoyl, and 4-bromobenzoyl) ; sulfonyl-containing groups (e.g., benzenesulfonyl, p- toluenesulfonyl, o-nitrobenzenesulfonyl, and p-nitrobenzenesulfonyl) ; carbamate forming groups (e.g., benzyloxycarbonyl , p-chlorobenzyloxycarbonyl, p-
• Preferred /V-protecting groups are acetyl, benzoyl, phenylsulfonyl, p- toluenesulfonyl, p-nitrobenzenesulfonyl, o-nitrobenzenesulfonyl, t-butyloxycarbonyl (Boc), and benzyloxycarbonyl (Cbz).
• 1 ,3-oxazolidin-2-one-5-yl is meant 1 ,3-oxazolidin-2-one-5-yl, in which the nitrogen atom is substituted with H or an /V-protecting group (e.g., Boc).
• pharmaceutically acceptable salt is meant a salt within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and animals without undue toxicity, irritation, allergic response and the like and commensurate with a reasonable benefit/risk ratio.
• Pharmaceutically acceptable salts are well known in the art. For example, pharmaceutically acceptable salts are described in: Berge et al., J. Pharmaceutical Sciences 66:1 -1 9, 1977 and in Pharmaceutical Salts: Properties, Selection, and Use, (Eds. P.H. Stahl and C.G. Wermuth), Wiley-VCH, 2008.
• Representative acid addition salts include acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptonate, glycerophosphate, hemisulfate, heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, 2-hydroxy-ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pe
• a preferred salt is the mesylate salt.
• sil is meant -SiR 3 , where each R is independently alkyl, alkenyl, aryl, or arylalkyi.
• Examples of silyl groups include tri(C 1 . 6 alkyl)silyl, tri(C 6 -io aryl or Ci -6 heteroaryl)silyl, di(C 6 -io aryl or Ci -6 eteroaryl)(Ci -6 alkyl)silyl, and (C 6- io aryl or d- 6 heteroaryl)di(C 1 . 6 alkyl)silyl.
• silyl group when a silyl group includes two or more alkyl, alkenyl, aryl, heteroaryl, or arylalkyi groups, these groups are independently selected.
• any heteroaryl group present in a silyl group has from 1 to 4 heteroatoms selected independently from 0, N, and S.
• Silyl can be optionally substituted in the same manner as defined for each R group.
• silene is meant -SiR 2 - where each R is independently alkyl, alkenyl, aryl, arylalkyi, or alkoxy.
• dialkylsilylene is meant a silylene, where each R is alkyl. Silylene can be optionally substituted in the same manner as defined for each R group.
• strong base is meant a Bransted base, the conjugate acid of which has pKa that is greater than or equal to 13.
• strong bases include alkyl alkali metals (e.g., butyl lithium or Schlosser's base), Grignard reagents (e.g., alkyl magnesium halide), alkoxides (e.g., tertiary alkoxides, such as f-butoxide), amides (e.g., diisopropylamide, tetramethylpiperidide, or bis(trimethylsilyl)amide), and phosphazene bases (e.g., Schwesinger base).
• alkyl alkali metals e.g., butyl lithium or Schlosser's base
• Grignard reagents e.g., alkyl magnesium halide
• alkoxides e.g., tertiary alkoxides, such as f-butoxide
• amides e
• sulfonamide is meant -NR, where R is sulfonyl.
• sulfonate is meant -OS(0) 2 R, where R is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyi.
• R is C 1-12 alkyl (e.g., C 1-8 , C 1 -6 , C 1-4 , C 2 _7, C 3 -i 2 , or C 3 - 6 alkyl), C 2 . 12 alkenyl (e.g., C 2 . 8 , C 2 . 6 , C 2 . 4 , C 3 -i 2 , or C 3 .
• any heteroaryl group present in a sulfonate group has from 1 to 4 heteroatoms selected independently from 0, N, and S.
• sulfonyl is meant -S(0) 2 R, where R is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, optionally substituted arylalkyi, or silyl.
• R is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, optionally substituted arylalkyi, or silyl.
• Preferred R groups for sulfonyl are the same as those described above for sulfonates.
• thioacetal is meant -S-(CHR)-S- where R is H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyi.
• thioketal is meant -S-(CR 2 )-S- where each R is independently optionally substituted alkyl, optionally substituted alkenyl, optionally substituted aryl, or optionally substituted arylalkyi.
• triflate is meant trifluoromethanesulfonate.
• the pKa values recited herein refer to the pKa values of a conjugate Bransted acid in water at room temperature, unless stated otherwise.
• Figure 1 is a scheme showing preparation of eribulin through a C.15-C.16 bond-forming macrocyclization.
• Figure 2 is a scheme showing preparation of eribulin through a C.2-C.3 bond-forming macrocyclization.
• Figure 3 is a scheme showing preparation of eribulin through a C.3-C.4 bond-forming macrocyclization.
• Figure 4 is a scheme showing preparation of eribulin through a C.19-C.20 bond-forming macrocyclization.
• Figure 5 is a scheme showing preparation of eribulin through a C.0-C.1 bond-forming macrocyclization.
• Figure 6 is a scheme showing preparation of eribulin through a C.26-C.27 bond-forming macrocyclization.
• Figure 7 is a depiction of a co-crystal of 2-((2R,3S,3aS,4aS,7R,8aR,9S,9aS)-2-((2,2-dimethyl-1 ,3- dioxolan-4-yl)methyl)-3,9-dihydroxydecahydrofuro[3,2-b]pyrano[2,3-e]pyran-7-yl)ethyl pivalate and its C3- epimer.
• the present invention provides methods for the synthesis of eribulin or a pharmaceutically acceptable salt thereof (e.g., eribulin mesylate) through a macrocyclizations.
• the macrocyclizations of the present invention involve subjecting a non-macrocyclic intermediate to a carbon-carbon bond-forming reaction (e.g., catalytic Ring-Closing Olefin Metathesis, an olefination reaction (e.g., Horner-Wadsworth-Emmons olefination), Nozaki-Hiyama-Kishi reaction, or Dieckmann reaction) to afford a macrocyclic intermediate (e.g., a compound of formula (IB), (MB), (I IIB), (IVB), (VB), or (VIB)).
• a carbon-carbon bond-forming reaction e.g., catalytic Ring-Closing Olefin Metathesis, an olefination reaction (e.g., Horner-Wadsworth-E
• the carbon-carbon bond forming reaction provides a C.0-C.1 , C.2-C.3, C.3-C.4, C.15-C.16, C.19-C.20, or C.26-C.27 bond in the structure of eribulin or a pharmaceutically acceptable salt thereof.
• the carbon-atom numbering scheme for eribulin and pharmaceutically acceptable salts thereof is shown in Chart 1 .
• the invention also provides intermediates in the synthesis of eribulin and methods of preparing the same, as described herein.
• the macrocyclization reaction of the invention can be a carbon-carbon bond-forming reaction (e.g., catalytic Ring-Closing olefin Metathesis (RCM)) that provides a C.15-C.16 bond in eribulin or a pharmaceutically acceptable salt thereof (e.g., eribulin mesylate).
• RCM catalytic Ring-Closing olefin Metathesis
• the general synthetic sequence including RCM that can be used to prepare eribulin or a pharmaceutically acceptable salt thereof (e.g., a mesylate salt) is shown in Figure 1 .
• the non-macrocyclic intermediate in the synthesis of eribulin can be a compound of formula (IA) :
• R 2 is H or a hydroxyl protecting group
• R 3 is Ci -6 alkyl ether
• R 4 is H ;
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond; or
• R 5 is H or a hydroxyl protecting group, and R 6 and R 7 combine to form a double bond; or
• R 8 is H, and P 4 is H or a hydroxyl protecting group
• each P 3 is independently H or a hydroxyl protecting group
• each of and P 2 is independently H or a hydroxyl protecting group, or
• X is N, and Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• An intermediate in the synthesis of eribulin can be a compound of formula (IB), which can be produced by reacting the compound of formula (IA) with an olefin metathesis catalyst (e.g., a ruthenium-carbene complex).
• an olefin metathesis catalyst e.g., a ruthenium-carbene complex.
• the compound of formula (IB) has the following structure:
• the catalysts that can be used to convert the compound of formula (IA) to the compound of formula (IB) can be those known in the art.
• Olefin metathesis catalysts include Ru-carbene complexes (e.g., Grubbs and Hoveyda-Grubbs catalysts).
• the compound of formula (IB) can be reacted with a hydroxyl protecting group removing agent and, optionally, an oxidizing agent (e.g., when R 8 is H in the compound of formula (IB)) capable of converting an alcohol to a carbonyl group (e.g., capable of converting an allylic alcohol to an enone) to afford the compound of formula (IC) :
• a hydroxyl protecting group removing agent e.g., when R 8 is H in the compound of formula (IB)
• an oxidizing agent capable of converting an alcohol to a carbonyl group (e.g., capable of converting an allylic alcohol to an enone)
• the hydroxyl protecting group removing agent used in the step forming the compound of formula (IC) can be a Bransted acid (e.g. , a carboxylic acid, such as a carboxylic acid having a pKa of 4 ⁇ 1 ) .
• the compound of form ula ( ID) can be prepared from the compound of form ula (IC) by a synthesis involving reacting the compound of form ula (IC) with a 1 ,4-reducing agent to afford a compound of form ula (ID) :
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal.
• the 1 ,4-reducing agents include copper (I) hydrides, which can be isolated (e.g., Stryker's reagent) or prepared in situ (e.g. , from a copper (I) or copper (I I) salt and a hydride source) .
• Catalytic quantities of a copper salt either copper (I) or copper (I I) salt
• a hydride source e.g., a borohydride salt, borane, PMHS, or a hydrosilane (e.g. , Ph 2 SiH 2 )
• X is 0, and each of P-i and P 2 is H ,
• Pi is H, and X and P 2 combine to form optionally masked amino.
• the compound of formula (ID) (e.g., the compound of formula (ID), in which X is 0, P 2 is H, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be aminated to afford eribulin, e.g., using sulfonylation followed by the treatment with a nitrogen source (e.g., ammonia (e.g., aqueous ammonia) or sulfamic acid).
• a nitrogen source e.g., ammonia (e.g., aqueous ammonia) or sulfamic acid.
• the nitrogen source is not ammonia or sulfamic acid, further contacting with an amino unmasking agent may be used to afford eribulin.
• the compound of formula (ID), in which P ⁇ is a hydroxyl protecting group, can be reacted with a hydroxyl protecting group removing agent prior to the amination reaction.
• the compound of formula (ID) in which P ⁇ is H, X and P 2 combine to form a masked amino, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal
• Eribulin mesylate can then be produced by salification of eribulin with methanesulfonic acid. The details of the amination and salification reactions are described below.
• the compound of formula (IA) can be prepared from a compound of formula (IE) :
• P is H or -CH 2 X 1 CH 2 CHCH 2 , wherein is 0, -C(R 9 ) 2 - or N P 5 , and where each R 9 is independently H or -COOR 10 , P5 is an /V-protecting group, and R 10 is Ci -6 alkyl;
• R 2 is H or a hydroxyl protecting group, R 3 is C 1 -6 alkyl ether, and R 4 is H ;
• R 2 is H or a hydroxyl protecting group, and R 3 and R 4 combine to form a double bond; or
• R 5 is H or a hydroxyl protecting group, and R 6 and R 7 combine to form a double bond; or
• R 5 and R 6 combine to form a bond, and R 7 is H ;
• R 8 is H , and P 4 is H or a hydroxyl protecting group;
• each P 3 is independently H or a hydroxyl protecting group
• Y is S0 2 Rn and Rn is optionally substituted aryl or optionally substituted non-enolizable alkyl ;
• Y is COOR , and Rn is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl ;
• X 3 is oxo, or X 3 , together with the carbon atom to which it is attached, forms -(CH(OH))-; and X is 0, and
• each of and P 2 is independently H or a hydroxyl protecting group, or
• X is N .
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• PT and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• the preparation of the compound of formula (IA) from the compound of formula (IE) involves a decarboxylation reaction (when X 3 is oxo, and Y is COOR ) or a desulfonylation (when X 3 is oxo, and Y is S0 2 Rn ) reaction.
• the conditions for the decarboxylation or desulfonylation reaction can be those described herein.
• the preparation of the compound of formula (IA) from the compound of formula (IE) can further involve oxidizing the compound of formula (IE) (e.g.
• the macrocyclization reaction of the invention can be a carbon-carbon bond-forming reaction (e.g., Horner-Wadsworth-Emmons reaction) that provides a C.2-C.3 bond in eribulin or a pharmaceutically acceptable salt thereof (e.g ., eribulin mesylate) .
• the general synthetic sequence including the Horner- Wadsworth-Emmons reaction that can be used to prepare eribulin or a pharmaceutically acceptable salt thereof (e.g. , a mesylate salt) is shown in Figure 2.
• the non-macrocyclic intermediate can be a compound of form ula (I IA) :
• each R is independently optionally substituted alkyl or optionally substituted aryl ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• P 4 is H or a hydroxyl protecting group
• each of ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• PT and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• the intermediate in the synthesis of eribulin can be a compound of formula (I I B) , which can be produced from the compound of formula (I IA) using Horner-Wadsworth-Emmons reaction.
• the compound of formula (I I B) has the following structure:
• reaction conditions that can be used to convert the compound of formula (IIA) into the compound of formula (MB) include those known in the art for Horner-Wadsworth-Emmons reaction, e.g., Masamune- Roush conditions or Helquist protocol.
• the compound of formula (IIA) can be reacted with an organic base (e.g., an organic base, the conjugate acid of which has a pKa of from 11 ⁇ 2) and a Lewis acid (e.g., a salt of Li, Mg, or Zn).
• an organic base e.g., an organic base, the conjugate acid of which has a pKa of from 11 ⁇ 2
• a Lewis acid e.g., a salt of Li, Mg, or Zn
• Non-limiting examples of an organic base that can be used in the Horner-Wadsworth-Emmons reaction include trialkylamines (e.g., triethylamine or Hunig's base), DBU, and DBN.
• Non-limiting examples of Lewis acids that can be used in the Horner-Wadsworth-Emmons reaction include LiCI, Zn(OTf) 2 , and MgCI 2 .
• the compound of formula (MB) can be converted to a compound of formula (ID):
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal; and
• each of Pi and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• the synthesis of the compound of formula (ID) from the compound of formula (IIB) can involve reacting the compound of formula (IIB) (e.g., the compound of formula (I IB), in which P 4 is a protecting group, P and R 2 form a bond, and R 3 is H) with a hydroxyl protecting group removing agent.
• the compound of formula (IIB) e.g., the compound of formula (I IB), in which P 4 is a protecting group, P and R 2 form a bond, and R 3 is H
• P 4 is a protecting group
• P and R 2 form a bond
• R 3 is H
• the compound of formula (ID) (in which X is 0, and P 2 are H, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be aminated to afford eribulin, as described herein.
• the compound of formula (ID) (in which P ⁇ is H, X and P 2 combine to form a masked amino, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be reacted with an amino unmasking agent to afford eribulin, as described herein.
• Eribulin mesylate can be produced by salification of eribulin, as describen herein.
• the compound of formula (IIA) can be prepared from a compound of formula (IIC) :
• R 4 is OH, and R 5 is H, or R 4 and R 5 combine to form a double bond;
• R 6 is -OP 5 or CH 2 P(0)(OR 6 ) 2 , where P 5 is an ether hydroxyl protecting group, and each R 6 is independently optionally substituted alkyl or optionally substituted aryl;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and
• P 4 is H or a hydroxyl protecting group; and X is 0, and
• each of and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• the preparation of the compound of formula (I I A) from the compound of form ula (I IC) can involve perform ing hydroboration/oxidation reaction on the compound of form ula (I IC) (e.g. , the compound of form ula (I IC) , in which R 4 and R 5 combine to form a double bond ; P and R 2 combine to form a bond ; and R 3 is H) .
• the preparation may involve subjecting the compound of formula (I IC) (e.g., the compound of formula (I IC) , in which R 6 is -OP 5 ) to a phospha-Claisen reaction with CH 3 P(0)(OR 6 ) 2 .
• Phospha-Claisen reaction conditions can be those known in the art. In a non-limiting example,
• CH 3 P(0)(OR 6 ) 2 can be deprotonated (e.g., by a contact with a strong base) and subsequently contacted with the compound of formula (I IC) .
• the preparation may also involve oxidizing the compound of formula (I IC) (e.g. , the compound of formula (I IC) , in which R 4 is OH , R 5 is H , and R 6 is CH 2 P(0)(OR 6 ) 2 ), e.g., by contacting this product with an oxidizing agent capable of oxidizing an alcohol to a carbonyl group.
• the compound of form ula ( I IC) can be prepared from a compound of formula (VI I E) , the compound of formula (VI IE) having the following structure:
• Yi is S0 2 Ri and RT is optionally substituted non-enolizable alkyl or optionally substituted aryl, or is COORT , and RT is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl ; or , where ⁇ is oxo, and R 4 is CHO ; and
• each of ⁇ and P 2 is independently H or a hydroxyl protecting group, or Pi and P 2 , together with the atoms to which each is attached, combine to form a cyclic protected diol ;
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• the compound of form ula (I IC) is prepared by reacting the compound of formula
• VI I E (e.g., the compound of formula (VI IE) , in which R 2 is , and is oxo) with a compound of form ula (I ID) , the compound of formula (I I D) having the following structure:
• R 4 is OH or OP 5 , and R 5 is H , or R 4 and R 5 combine to form a double bond ;
• each P 3 , P 4 , and P 5 is independently a hydroxyl protecting group
• Y is chloro, bromo, iodo, or trifluoromethanesulfonate.
• the macrocyclization reaction of the invention can be a carbon-carbon bond-forming reaction (e.g., catalytic Ring-Closing olefin Metathesis (RCM)) that provides a C.3-C.4 bond in eribulin or a
• X 3 is oxo, or X 3 combines with the carbon atom to which it is attached to form a ketal, a thioketal, or -(CH(OP 5 ))-, wherein P 5 is H or a hydroxyl protecting group;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• P 4 is H or a hydroxyl protecting group
• each of ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• PT is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• An intermediate in the synthesis of eribulin can be a compound of form ula (I I I B) , which can be produced by reacting the compound of form ula (I I IA) with an olefin metathesis catalyst (e.g. , a ruthenium-carbene complex) .
• the compound of formula (I I IB) has the following structure:
• the catalysts that can be used to convert the compound of formula (II IA) to the compound of formula (I IIB) can be those known in the art.
• Olefin metathesis catalysts include Ru-carbene complexes (e.g., Grubbs and Hoveyda-Grubbs catalysts).
• the compound of formula (II IB) can be converted to a compound of formula (ID), from which eribulin or eribulin mesylate can be prepared as described herein.
• a compound of formula (ID) from which eribulin or eribulin mesylate can be prepared as described herein.
• a non-limiting example of the preparation of the compound of formula (ID) from the compound of formula (I IIB) is provided below.
• Oxidation of the -(CH(OH))- in the compound of formula (I IIB) to give the compound of formula (I IIB), in which X 3 is oxo, can be performed using methods known in the art for oxidation of alcohols to carbonyl groups, e.g., by contacting the compound of formula (I IIB) with an oxidizing agent capable of converting an alcohol to a carbonyl group.
• the compound of formula (II IB) (e.g., the compound of formula (II IB), in which X 3 is oxo, and is a hydroxyl protecting group) can be reacted with a hydroxyl protecting group removing agent to afford a compound of formula (ID) :
• each P 3 is H, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal;
• X is 0, and P-i and P 2 are H ;
• Pi is H, and X and P 2 combine to form optionally masked amino.
• the conditions for the reaction used in preparing the compound of formula (ID) from the compound of formula (1MB) can be those allowing for isomerization of a ⁇ , ⁇ -enone to an ⁇ , ⁇ -enone (e.g., including basic or acidic compounds).
• a hydroxyl protecting group removing agent such as a fluoride source (e.g., TBAF)
• TBAF fluoride source
• the compound of formula (ID) (in which X is 0, P ⁇ and P 2 are H, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be aminated to afford eribulin, as described herein.
• the compound of formula (ID) (in which P ⁇ is H, X and P 2 combine to form a masked amino, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be reacted with an amino unmasking agent to afford eribulin, as described herein.
• Eribulin mesylate can be produced by salification of eribulin, as describen herein.
• the compound of formula (II IA) can be prepared from a compound of formula (NIC) :
• F is H or a hydroxyl protecting group, and R 2 and R 3 combine to form a double bond; or
• X 3 is oxo and R 4 is H or OP 6 , or X 3 and R 4 combine with the carbon atom to which they are attached to form an acetal, a thioacetal, or -CH 2 OP 5 ; where P 5 is H or a hydroxyl protecting group, and P 6 is an ether hydroxyl protecting group;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal;
• P 4 is H or a hydroxyl protecting group
• each of Pi and P 2 is independently H or a hydroxyl protecting group
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• the preparation of the compound of formula (IIIA) from the compound of formula (IIIC) involves allylating the compound of formula (IIIC) (e.g., the compound of formula (IIIC), in which R 4 is H, and X 3 is oxo, or X 3 and R 4 combine with the carbon atom to which they are attached to form a thioacetal). Allylation of the compound of formula (IIIC) can be performed using conditions known in the art.
• allylation of the compound of formula (IIIC) can be a nucleophilic allylation (e.g., by contacting the compound of formula (IIIC) with a nucleophilic allylating agent (e.g., allylboron reagent (e.g., allyl boronate or allyl borane), allylstannane, allyl Grignard reagent, allylsilane, or allyl indium).
• a nucleophilic allylating agent e.g., allylboron reagent (e.g., allyl boronate or allyl borane), allylstannane, allyl Grignard reagent, allylsilane, or allyl indium.
• allylation of the compound of formula (IIIC) can be performed using electrophilic allylation (e.g., when X 3 and R 4 combine with the carbon to which they are attached to form a thioacetal).
• electrophilic allylation the compound of formula (IIIC), in which X 3 and R 4 combine with the carbon to which they are attached to form a thioacetal, can be contacted with a strong base followed by an allyl ic electrophile (e.g., allyl halide or allyl sulfonate).
• the preparation of the compound of formula (IIIA) from the compound of formula (IIIC) can also involve reducing the compound of formula (IIIC), in which X 3 is oxo and R 4 is OP 6 , with a 1 ,2-reducing agent to afford a compound of formula (IIIC), in which X 3 is oxo or -(CH(OH))-, and R 4 is H.
• Formation of the compound of formula (IIIC), in which X 3 is oxo, and R 4 is H, can be direct (e.g., by treating with DIBAL at a temperature between about -70 °C and about -80 °C) or indirect via the compound of formula (IIIC), in which X 3 combines with the carbon atom to which it is attached to form -(CH(OH))-, and R 4 is H.
• the indirect route to the compound of formula (IIIC), in which X 3 is oxo, and R 4 is H thus involves first reducing the compound of formula (IIIC), in which X 3 is oxo, and R 4 is OP 6 , with a 1 ,2-reducing agent to give the compound of formula (IIIC), in which X 3 combines with the carbon atom to which it is attached to form -(CH(OH))-, and R 4 is H.
• the latter compound can be reacted with an oxidizing agent capable of oxidizing an alcohol to a carbonyl group to furnish the compound of formula (IIIC), in which X 3 is oxo, and R 4 is H.
• the sensitive functional groups present in the compound of formula (IIIC) can be protected (e.g., Ri and each P 3 is independently a hydroxyl protecting group) or can be present in an unreactive form (e.g., both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) .
• the macrocyclization reaction of the invention can be a carbon-carbon bond-forming reaction (e.g., Nozaki-Hiyama-Kishi reaction (N H K)) that provides a C.1 9-C.20 bond in eribulin or a pharmaceutically acceptable salt thereof (e.g ., eribulin mesylate) .
• N H K Nozaki-Hiyama-Kishi reaction
• the general synthesis sequence including N H K that can be used to prepare eribulin or a pharmaceutically acceptable salt thereof (e.g. , a mesylate salt) is shown in Figure 4.
• the non-macrocyclic intermediate in the synthesis of eribulin can be a compound of form ula (IVA) :
• Y is iodide, brom ide, or trifluoromethanesulfonate
• R 2 is H or a hydroxyl protecting group, R 3 and R 4 combine to form a double bond ;
• R 2 and R 3 combine to form a bond, and R 4 is H ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• An intermediate in the synthesis of eribulin can be a compound of formula (IVB), which can be produced by subjecting the compound of formula (IVA) to Nozaki-Hiyama-Kishi reaction conditions (e.g., by reacting with a Cr(l l) salt and a Ni(l l) salt).
• the compound of formula (IVB) has the following structure:
• a designates ft stereogenic center
• b designates S stereogenic center
• Z is a sulfonate, chloride, bromide, or iodide
• a designates S stereogenic center
• b designates R stereogenic center
• Z is ORi , wherein is a hydroxyl protecting group.
• Nozaki-Hiyama-Kishi reaction conditions that may be used to prepare the compound of formula (IVB) from the compound of formula (IVA) can be those known in the art.
• Nozaki-Hiyama-Kishi reaction on the compound of formula (IVA) can include reacting the compound of formula (IVA) with a Cr(ll) salt and a Ni(l l) salt.
• Ancillary ligands can be used in combination with the metal salts.
• a substituted 1 ,10-phenanthroline can be used in combination with a Ni(l l) salt.
• Chiral ancillary ligands can be used to render the reaction stereoselective.
• chiral N-(dihydrooxazolyl- phenyl)-sulfonamides can be used with a Cr(l l) salt to control the stereochemistry of the carbonyl carbon, to which a vinyl nucleophile is added in the course of Nozaki-Hiyama-Kishi reaction.
• the compound of formula (IVB) can be converted to a compound of formula (ID), from which eribulin or erinulin mesylate can be prepared, as described herein.
• a non-limiting exemplary reaction sequence from the compound of formula (IVB) to the compound of formula (ID) is provided below.
• the compound of formula (IVB) can be converted to a compound of formula (ID) directly or via an intermediate of formula (IVC).
• the compound of formula (IVB) in which Z is an ester, a designates S stereogenic center, b designates R stereogenic center, can be converted to the compound of formula (IVC), e.g., by reacting with a sulfonyl electrophile, such as a sulfonyl chloride or a sulfonyl anhydride.
• Z is an ester
• R 2 is H or a hydroxyl protecting group, R 3 and R 4 combine to form a double bond; or
• R 2 and R 3 combine to form a bond, and R 4 is H ;
• R 5 is sulfonyl
• each P 3 is independently a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal;
• each of ⁇ and P 2 is independently a hydroxyl protecting group
• Pi is a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino.
• the preparation of the compound of formula (ID) from the compound of formula (IVC) can involve reacting the compound of formula (IVC) with a Ci -6 alkoxide.
• the compound of formula (ID) has the following structure:
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• each of Pi and P 2 is independently a hydroxyl protecting group
• Pi is a hydroxyl protecting group
• X and P 2 combine to form optionally masked am ino.
• the compound of form ula ( IVB) (in which Z is a sulfonate, chloride, brom ide, or iodide, a designates R stereogenic center, b designates S stereogenic center, R 2 and R 3 combine to form a bond, and R 4 is H) can be converted to the compound of form ula (I D) directly, e.g., upon isolation from the Nozaki-Hiyama- Kishi reaction m ixture (e.g ., by treatment with a base) or by contacting a m ixture containing the product of the Nozaki-Hiyama-Kishi reaction with silica gel.
• the compound of form ula ( ID) (e.g. , the compound of formula (ID) in which P ⁇ is a hydroxyl protecting group) can be reacted with a hydr to afford :
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• each of Pi and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• the compound of form ula ( ID) (in which X is 0, Pi and P 2 are H , and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be aminated to afford eribulin, as described herein.
• the compound of formula (ID) (in which P ⁇ is H , X and P 2 combine to form a masked am ino, and both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal) can be reacted with an am ino unmasking agent to afford eribulin, as described herein.
• Eribulin mesylate can be produced by salification of eribulin, as describen herein.
• the compound of form ula ( IVA) can be prepared from the compound of formula (IVD) :
• Y is iodide, brom ide, or trifluoromethanesulfonate
• ⁇ - ⁇ is H , COOR 6 , or S0 2 R 6 , where, when is COOR 6 , R 6 is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl, and, when Y ⁇ is S0 2 R 6 , R 6 is optionally substituted aryl or optionally substituted non-enolizable alkyl ;
• Z is an ester, a sulfonate, chloride, bromide, or iodide
• R 2 is H or a hydroxyl protecting group, R 3 and R 4 combine to form a double bond ;
• R 2 and R 3 combine to form a bond, and R 4 is H ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo; or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• X 3 is oxo, or X 3 combines with the carbon atom to which it is attached to form -(CH(OH))-;
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an am inal or 1 ,3-oxazolidin-2-one-5-yl.
• the preparation of the compound of formula (IVA) involves oxidizing the compound of form ula (IVD) , in which X 3 is -(CH(OH))-, and/or P 4 is H , e.g. , by reacting with an oxidizing agent capable of oxidizing an alcohol to a carbonyl group.
• the preparation of the compound of form ula (IVA) can also involve perform ing a decarboxylation or desulfonylation reaction on the compound of formula (IVA) , in which is COOR 6 (decarboxylation) or S0 2 R 6 (desulfonylation) .
• the compound of formula (IVD) can be prepared from a compound of formula (IVE) and the compound of form ula (VI I E) :
• the compound of form ula ( IVE) can have the following structure:
• R 7 is H or a hydroxyl protecting group, and R 8 and R 9 combine to form a double bond ;
• X 3 is oxo
• R 10 is H or -OP 5 , where P 5 is H or an ether hydroxyl protecting group; and the remaining variables are as defined in formula (IVD) .
• the compound of form ula (IVD) is prepared by reacting the compound of formula (IVE) (e.g., the compound of form ula (IVE) , in which X is oxo) with the compound of form ula (VI I E) which was pretreated with a strong base.
• IVE compound of formula
• VI I E compound of form ula
• the macrocyclization reaction of the invention can be a carbon-carbon bond-forming reaction (e.g., Dieckmann reaction) that provides a C.0-C.1 bond in eribulin or a pharmaceutically acceptable salt thereof (e.g. , eribulin mesylate) .
• Dieckmann reaction a carbon-carbon bond-forming reaction
• a pharmaceutically acceptable salt thereof e.g. , eribulin mesylate
• the general synthetic sequence including the Dieckmann reaction that can be used to prepare eribulin or a pharmaceutically acceptable salt thereof (e.g., a mesylate salt) is shown in Figure 5.
• the non-macrocyclic intermediate in the synthesis of eribulin can be:
• Y is S0 2 Ri or COORT , where, when Y is S0 2 Ri , R ⁇ is optionally substituted aryl or optionally substituted non-enolizable alkyl, and when Y is COOR ⁇ R- ⁇ is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl ;
• each P 3 is independently H or a hydroxyl protecting group, and X 2 is oxo, or both P 3 groups and X 2 , together with the atoms to which each is attached , combine to form ketal ;
• R 2 is optionally substituted alkyl, optionally substituted arylalkyl, or optionally substituted aryl ;
• each of P ⁇ and P 2 is independently a hydroxyl protecting group
• X is N , and Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;
• Pi and P 2 together with the atoms to which each is attached, combine to form an aminal or 1 ,3-oxazolidin-2-one-5-yl.
• An intermediate in the synthesis of eribulin can be a compound of formula (VB), which can be produced from the compound of formula (VA) using Dieckmann reaction.
• the compound of formula (VB) has the following structure:
• P P 2 , P 3 , X, X 2 , and Y are as defined for compound of formula (VA) ; and R 3 is H, R 4 is optionally substituted C 1 -6 alkyl ether, and R 5 is H ;
• R 5 is H, and R 3 and R 4 combine to form a double bond
• R 3 is H, and R 4 and R 5 combine to form a bond
• reaction conditions that can be used to convert the compound of formula (VA) into the compound of formula (VB) include those known in the art for the Dieckmann reaction or Claisen condensation.
• the compound of formula (VA) can be contacted with a strong base (e.g., a C 4 . 6 alkoxide) to afford the compound of formula (VB).
• a strong base e.g., a C 4 . 6 alkoxide
• the compound of formula (VB)(i) or (VB)(ii) can be converted to the compound of formula (VB)(iii) prior to the next step by contacting the compound of formula (I IB)(i) or (VB)(ii) with aqueous bicarbonate (e.g., during a work up of the Dieckmann reaction mixture) or with silica gel (e.g., by purification of the compound of formula (VB) by silica gel chromatography).
• aqueous bicarbonate e.g., during a work up of the Dieckmann reaction mixture
• silica gel e.g., by purification of the compound of formula (VB) by silica gel chromatography
• the compound of formula (VB) can be converted to the compound of formula (ID), from which eribulin or eribulin mesylate can be produced as described herein.
• the reaction sequence from the compound of formula (VB) to the compound of formula (ID) can include (i) a desulfonylation or a decarboxylation reaction and (ii) reactions with hydroxyl protecting group removing agent or an amino unmasking agent.
• the conditions for the decarboxylation reaction can be those known in the art, e.g., Krapcho decarboxylation or a sequence including deprotection (converting Ri to H) and
• the conditions for the desulfonylation reaction can be those known in the art.
• the desulfonylation reaction can include contacting the compound of formula (I IB), in which Y is SO 2 R 1 , with an electron-transferring reducing agent (e.g., Sm l 2 ; Cr(ll l) salt and Mn(0) ; or Mg(0)).
• an electron-transferring reducing agent e.g., Sm l 2 ; Cr(ll l) salt and Mn(0) ; or Mg(0).
• the compound of formula (ID) (e.g., the compound of formula (ID) in which P ⁇ is a hydroxyl protecting group) can be reacted with a hydroxyl protecting group removing agent to afford:
• X is O, and each of P ⁇ and P 2 is H ,
• Pi is H, and X and P 2 combine to form optionally masked amino.
• the compound of formula (ID) (in which X is 0, P-i and P 2 are H, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be aminated to afford eribulin, as described herein.
• the compound of formula (ID) (in which P ⁇ is H, X and P 2 combine to form a masked amino, and both P 3 groups and X 2 , together with the atoms to which each is attached, combine to form ketal) can be reacted with an amino unmasking agent to afford eribulin, as described herein.
• Eribulin mesylate can be produced by salification of eribulin, as describen herein.
• the compound of formula (VA) can be prepared from the compound of formula (VII E) :
• Y is S0 2 Ri or COOF , where, when Y is S0 2 Ri , FM is optionally substituted aryl or optionally substituted non-enolizable alkyl, and when Y is COOR1 , Ri is optionally substituted alkyl, optionally substituted aryl, or optionally substituted arylalkyl ;
• P 3 is H or a hydroxyl protecting group
• each of P ⁇ and P 2 is independently H or a hydroxyl protecting group, or
• Pi is H or a hydroxyl protecting group, and X and P 2 combine to form optionally masked amino;

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