WO2024201390A1

WO2024201390A1 - Methods and reagents for synthesizing haloaldehydes, and uses thereof

Info

Publication number: WO2024201390A1
Application number: PCT/IB2024/053061
Authority: WO
Inventors: Robert Britton; Juan Manuel Mesa BRUNO
Original assignee: Simon Fraser University
Priority date: 2023-03-29
Filing date: 2024-03-28
Publication date: 2024-10-03

Abstract

The present invention relates to methods and intermediates for the synthesis of haloaldehydes.

Description

METHODS AND REAGENTS FOR SYNTHESIZING HALOALDEHYDES, AND USES THEREOF

FIELD

[0001] The present invention relates to methods and intermediates for the synthesis of haloaldehydes.

BACKGROUND

[0002] Nucleosides play key roles in diverse cellular processes ranging from cell signalling to metabolism (1). Nucleosides are composed of a nucleobase - canonically composed of adenine, guanine, cytosine, thymine and uracil, and a sugar moiety, typically ribose of 2’- deoxyribose. Nucleosides can be further modified with a 5’-phosphate or phosphate-like group, and RNA oligomers include nucleotides linked via phosphate or phosphate-like linkages from 5’ to 3’. Nucleosides can be modified in several ways, including modifications to the ribose moiety, modifications to the base moiety or modifications to the phosphate moiety, leading to compounds referred to as “nucleoside analogues” (NAs).

[0003] NAs have a long and rich history in the field of medicinal chemistry and as tool compounds in chemical biology. The naturally occurring nucleosides are a unique and valuable starting point for drug design due to their involvement in numerous biological processes. Synthetic NAs have been designed to mimic their natural counterparts (2-18). Single NAs have been primarily used as treatments for parasitic, bacterial and fungal infections as well as potent and effective anticancer drugs. In addition to this “small molecule” modality, NAs can be incorporated into oligomeric structures that can modulate gene expression, thus bypassing the complexities associated with protein inhibition. Such oligomeric structures can include short interfering RNA (siRNA), microRNA (miRNA), inhibitory antisense oligonucleotides (ASOs), small activating RNA (saRNA) and messenger RNA (mRNA).

[0004] NAs have been used in the treatment of cancer (2, 6) and represent the largest class of small molecule antivirals (3, 4). Mechanistically, NAs can operate as toxic antimetabolites that interfere with nucleic acid synthesis (4). Alternatively, following in vivo phosphorylation, the resulting nucleotide analogues can inhibit enzymes involved in cancer cell growth or viral replication (e.g., DNA/RNA polymerases, ribonucleotide reductases or nucleoside phosphorylases) (2, 4). NAs have also demonstrated promise as epigenetic modulators, and both decitabine and azacitidine inhibit DNA methyltransferase and have been approved for cancer therapy (4). [0005] While several decades of organic and medicinal chemistry have yielded numerous valuable nucleoside analogues, the synthesis of further nucleoside analogues presents some challenges. Nucleoside analogues are often synthesized from naturally occurring carbohydrate, which limits patterns of substitution and furanose stereochemistry (e.g., 19- 29). The addition of nucleobases to activated ribose derivatives often fails or proceeds with poor diastereoselectivity with C2’ or C4’ modified nucleosides and efficient strategies for producing C4’ modified nucleosides, including thionucleosides are limited. Synthesis of nucleosides and nucleoside analogues have been described in Meanwell et a/., (30) and WO 2021/191830.

SUMMARY

[0006] The present invention relates to methods and intermediates for the synthesis of haloaldehydes.

[0007] In one aspect, the present invention provides a method of synthesizing a haloaldehyde compound by reacting a halogen or halogen-containing compound with an aryl- or heteroaryl-substituted compound in the presence of a catalyst compound according to Formula (I):

Formula (I) where Ri, R2, R3, and R4 may each independently be H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and Cx may be a salt counterion, to yield the haloaldehyde compound.

[0008] In an alternative aspect, the present invention provides a method of preparing an intermediate in the synthesis of a nucleoside or analogue thereof by reacting a halogen or halogen-containing compound with an aryl- or heteroaryl-substituted compound in the presence of a catalyst compound according to Formula (I):

Formula (I) where Ri, R₂, R3, and R₄ may each independently be H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and Cx may be a salt counterion; and performing an enantioselective aldol reaction by proline catalysis to yield a halohydrin compound that is an intermediate in the synthesis of a nucleoside or analogue thereof. In some embodiments, the method may further include reducing the halohydrin compound to obtain a halohydrin diol compound.

[0009] In an alternative aspect, the present invention provides a method of synthesizing a nucleoside or analogue thereof by reacting a halogen or halogen-containing compound with an aryl- or heteroaryl-substituted compound in the presence of a catalyst compound according to Formula (I):

Cx

Formula (I) where R1, R₂, R3, and R₄ may each independently be H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and Cx may be a salt counterion; performing an enantioselective aldol reaction by proline catalysis to yield a halohydrin compound; reducing the halohydrin compound to yield a halohydrin diol compound; and contacting the halohydrin diol compound with a Lewis acid or a base in an annulative halide displacement (AHD) reaction, to yield a nucleoside or analogue thereof.

[0010] In some embodiments, the halogenation may be enantioselective.

[0011] In some embodiments, the proline may be L-proline or D-proline. In some embodiments, the proline may be a halophilic Lewis acid.

[0012] In some embodiments, the Lewis acid may be lnCI₃ or Sc(OTf)₃. [0013] In some embodiments, the Lewis acid-promoted AHD may yield a C2',C3'-protected nucleoside or analogue thereof, a nucleoside or analogue thereof with a migrated acetonide protecting group, or results in deprotection.

[0014] In some embodiments, the halohydrin diol compound may be separated prior to treatment with the base.

[0015] In some embodiments, the base may be NaOH, K₂CO₃, KHCO₃, Na₂CO₃, NaHCO₃, KOH, LiOH, Li₂CO₃, LiHCO₃, Cs₂CO₃, CsHCO₃, or CsOH.

[0016] In some embodiments, the base-promoted AHD may yield a C3’,C5’-protected nucleoside or analogue thereof.

[0017] In some embodiments, the halohydrin compound may be:

where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl, and X may be a halogen.

[0018] In some embodiments, the halohydrin compound may be:

[0019] In some embodiments, the halohydrin diol compound may be:

[0020] In some embodiments, the halogen may be fluorine, bromine, chlorine, or iodine.

[0021] In some embodiments, the halogen-containing compound may be an electrophilic halogenating agent, such as N-Fluorobenzenesulfonimide (NFSI), Selectfluor™, Xtalfluor™, N-halosuccinimide, N-chlorinated hydantoin, Palau’chlor™, or N-fluoropyridinium.

[0022] In some embodiments, the salt counterion may be HCI, TFA, HBr, or MsOH.

[0023] In some embodiments, the catalyst compound may be:

[0024] In some embodiments, the aryl- or heteroaryl- substituted compound may include the following chemical structure:

or

where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl.

[0025] In some embodiments, the haloaldehyde compound may include the following chemical structure:

_H -^NB where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl, X may be a halogen, and * refers to enantioenrichment.

[0026] In some embodiments, the haloaldehyde compound is may be:

[0027] In some embodiments, the nucleoside or analogue thereof may be:

, or where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl and each R may be independently -OH, -OC(CH3)2O-, -(CH2)3-, - CH2SCH2-, or -CH₂OCH₂-.

[0028] In some embodiments, the nucleoside or analogue thereof may be a C3VC5' protected NA, a C4' modified NA, a C2' modified NA, a C-linked NA, a L-configured NA, a D- nucleoside or analogue thereof, a L-nucleoside or analogue thereof, a locked nucleic acid, an iminonucleoside, or a thionucleoside.

[0029] In an alternative aspect, the present invention provides a halohydrin compound that is:

[0030] This summary of the invention does not necessarily describe all features of the invention.

DETAILED DESCRIPTION

[0031] The present disclosure provides, in part, methods for the synthesis of a haloaldehyde compound and uses thereof.

[0032] In some embodiments, the method for the synthesis of a haloaldehyde compound includes reacting a halogenating agent (a halogen or halogen-containing compound) with an aryl- or heteroaryl-substituted compound in the presence of a catalyst compound according to Formula (I):

Cx

Formula (I) where Ri, R₂, R3, and R₄ may each independently be H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and Cx may be a salt counterion.

[0033] By an “aryl- or heteroaryl- substituted compound,” as used herein, is meant a compound having a structure as follows:

or

[0034] A catalyst compound, as used herein, is a compound according to Formula (I):

Cx

Formula (I) where R1, R₂, R3, and R₄ may each independently be H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and Cx may be a salt counterion.

[0035] In some embodiments, a catalyst compound in accordance with the present disclosure may be “enantiopure” or “enantioenriched.”

[0036] In some embodiments, a catalyst compound in accordance with the present disclosure may include, without limitation, the following compounds:

[0037] By “haloaldehyde compound” or “haloaldehyde,” as used herein, is meant a compound containing a functional group in which a halogen and an aldehyde, e.g, an acetaldehyde, are bonded to adjacent groups. A haloaldehyde can have the following the general structure:

or

* = enantioenriched where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl; and X may be a halogen.

[0038] In some embodiments, haloaldehyde compounds may include, without limitation, the following compounds:

[0039] “Alkyl” refers to a straight or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, containing no unsaturation and including, for example, from one to ten carbon atoms, or any value in between, such as 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, and which is attached to the rest of the molecule by a single bond. In some embodiments, alkyl may refer to a straight or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, containing no unsaturation and including from one to six carbon atoms, or any value in between, such as 1 , 2, 3, 4, 5, or 6 carbon atoms, and which is attached to the rest of the molecule by a single bond. Unless stated otherwise specifically in the specification, the alkyl group may be optionally substituted by one or more substituents as described herein. Unless stated otherwise specifically herein, it is understood that the substitution can occur on any carbon of the alkyl group.

[0040] “Acyl” refers to a group of the formula -C(O)R_a, where R_a is a C1-10 alkyl or a Ci-₆ alkyl group as described herein. The alkyl group may be optionally substituted as described herein.

[0041] By “aryl” is meant a monocyclic or bicyclic aromatic ring containing only carbon atoms, including for example, 5-14 members, such as 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, or 14 members. Examples of aryl groups include without limitation phenyl, biphenyl, naphthyl, indanyl, indenyl, tetrahydronaphthyl, 2,3-dihydrobenzofuranyl, dihydrobenzopyranyl, 1 ,4- benzodioxanyl, and the like. Unless stated otherwise specifically herein, the term “aryl” is meant to include aryl groups optionally substituted by one or more substituents as described herein. [0042] “Heteroaryl” refers to a single or fused aromatic ring group containing one or more heteroatoms in the ring, for example N, O, S, including for example, 5-14 members, such as 5, 6, 7, 8, 9, 10, 11 , 12, 13, or 14 members. Examples of heteroaryl groups include without limitation furan, thiophene, pyrrole, oxazole, thiazole, imidazole, pyrazole, isoxazole, isothiazole, 1 ,2,3-oxadiazole, triazole (e.g., 1 ,2,3-triazole or 1 ,2,4-triazole), 1 ,3,4-thiadiazole, tetrazole, pyrazole, pyridine, pyridazine, pyrimidine, 2,6-dichloropyrimidine pyrazine, 1 ,3,5- triazine, imidazole, benzimidazole, benzoxazole, benzothiazole, indolizine, indole, isoindole, benzofuran, benzothiophene, 1 H-indazole, purine, 4H-quinolizine, quinoline, isoquinoline, cinnoline, phthalazine, quinazoline, quinoxaline, 1 ,8-naphthyridine, pteridine, uracil, thymine, deazadenine, phthalimide, adenine, and the like. Unless stated otherwise specifically herein, the term “heteroaryl” is meant to include heteroaryl groups optionally substituted by one or more substituents as described herein.

[0043] By “arylalkyl” is meant a group of the formula -R_aR_b where R_a is a C1-10 alkyl group as described herein and R_b is one or more aryl moieties as described herein. The arylalkyl group(s) may be optionally substituted as described herein. Examples of arylalkyl groups include without limitation benzyl, phenethyl, phenylpropyl, (4-methylphenyl)methyl, (4- methylphenyl)ethyl, (2-methylphenyl)methyl, (2,4,6-trimethylphenyl), etc.

[0044] “Heteroarylalkyl” refers to a group of the formula -R_aR_c where R_a is a C1-10 alkyl group as described herein and R_c is one or more heteroaryl moieties as described herein. The heteroarylalkyl group(s) may be optionally substituted as described herein. Examples of heteroarylalkyl groups include without limitation, furanylmethyl, thiphenylmethyl, pyridylmethyl, imidazolylmethyl, uridinylmethyl, etc.

[0045] “Cx” refers to a salt counterion. In some embodiments, Cx may be without limitation hydrochloric acid (HCI), trifluoroacetic acid (TFA), hydrobromic acid (HBr), methanesulfonic acid (MsOH), etc.

[0046] “X” refers to a halogen, such as bromine, chlorine, fluorine, iodine, etc. In some embodiments, a halogen may include chlorine or fluorine. According, “halo” refers to bromo, chloro, fluoro, iodo, etc. A halide is a halogen atom bearing a negative charge. By “halogenating” is meant introducing a halogen atom into a compound or molecule. It is to be understood that a halogen may be in a “halogen-containing compound”, for example, N- Fluorobenzenesulfonimide (NFSI), Selectfluor™, Xtalfluor™, N-halosuccinimide (e.g., N- chlorosuccinimide (NCS)), N-chlorinated hydantoins, Palau’chlor™, N-fluoropyridinium salts, etc. In some embodiments, a halogen-containing compound may be an electrophilic halogenating agent. Accordingly, a halogen, as used herein, includes a halogen-containing compound or “halogenating agent.”

[0047] “Optional” or “optionally” means that the subsequently described event of circumstances may or may not occur, and that the description includes instances where the event or circumstance occurs one or more times and instances in which it does not. For example, “optionally substituted alkyl” means that the alkyl group may or may not be substituted and that the description includes both substituted alkyl groups and alkyl groups having no substitution, and that the alkyl groups may be substituted one or more times. Examples of optionally substituted alkyl groups include, without limitation, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, etc. Examples of suitable optional substituents include, without limitation, H, F, Cl, CH3, OH, OCH3, CF3, CHF2, CH2F, CN, halo, and C1-10 alkoxy. Similarly, “optionally substituted aryl- or heteroaryl-” means aryl- or heteroaryl- groups that may or may not be substituted and that the description includes both substituted aryl- or heteroaryl- groups and aryl- or heteroaryl- groups having no substitution, and that the aryl- or heteroaryl- groups may be substituted one or more times. Examples of suitable optional substituents include, without limitation, H, F, Cl, CH₃, OH, OCH3, CF₃, CHF₂, CH₂F, CN, halo, and C1-10 alkoxy.

[0048] In some embodiments, the present disclosure includes a method for the synthesis of a haloaldehyde compound for example in accordance with Scheme 1 :

= enantioenriched

Scheme 1

[0049] In Scheme 1 , R1, R2, R3, and R4 may each independently be H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and Cx may be a salt counterion, of the catalyst compound according to Formula (I); NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl; X may be halogen and X+ may be an electrophilic halogenating agent (for example, NFSI, NCS, etc).

[0050] In some embodiments, the haloaldehyde compound may be used to prepare a halohydrin compound, for example in accordance with Scheme 2:

= enantioenriched

Scheme 2

[0051] In Scheme 2, NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl; X may be halogen; Y may be CH₂, O, S, NR’, where R’ may be alkyl or aryl, and Z may be a protecting group for an alcohol, including without limitation, acetonide, silyl protecting group, alkyl protecting group or aryl protecting group (including cyclic or acyclic).

[0052] By “halohydrin” is meant a compound containing a functional group in which a halogen and a hydroxyl are bonded to adjacent groups. A halohydrin can have the following the general structure, where R may be any suitable group, and X may be halogen:

[0053] In some embodiments, the halohydrin compound may have the following general structure, where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl and X may be halogen:

[0054] In some embodiments, the halohydrin compound may be:

[0055] In some embodiments, the halohydrin diol compound may have the following general structure, where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl and X may be halogen:

[0056] In some embodiments, the halohydrin compound may be used in the synthesis of a nucleoside or analogue thereof, for example, in accordance with Scheme 3:

* = enantioenriched

* = enantioenriched * = enantioenriched

Scheme 3

[0057] In Scheme 3, NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl; X may be halogen; Y may be CH₂, O, S, NR’, where R’ may be alkyl or aryl, and Z may be a protecting group for an alcohol, including without limitation, acetonide, silyl protecting group, alkyl protecting group or aryl protecting group (including cyclic or acyclic).

[0058] In some embodiments, the compounds disclosed herein, such as catalyst compounds, haloaldehydes, halohydrins, etc. may be enantiopure or enantioenriched, i.e, available predominantly in a single, specific enantiomeric form or “enantioenrichment.” For haloaldehydes, halohydrins, etc., enantiomeric purity or enrichment will depend on the stereochemistry of the catalyst compound. It is to be understood that, while full enantiomeric purity or enrichment is not required, an enantiopure or enantioenriched compound in accordance with the present disclosure may be at least 95% enantioenriched. In some embodiments, the enantiopure or enantioenriched compound in accordance with the present disclosure is fully i.e., 100% enriched. Accordingly, methods of obtaining enantiopure or enantioenriched compounds are referred to herein as “enantioselective” or “enantioselection” reactions.

[0059] In some embodiments, the present disclosure provides a method of preparing an intermediate in the synthesis of a nucleoside or analogue thereof, the method comprising: reacting a halogen or halogen-containing compound with an aryl- or heteroarylsubstituted compound in the presence of a catalyst compound according to Formula (I): Cx

Formula (I) where Ri, R₂, R3, and R₄ may each independently be H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and Cx may be a salt counterion; performing an enantioselective aldol reaction by proline catalysis to yield a halohydrin compound; and reducing the halohydrin compound to obtain a halohydrin diol compound, to yield an intermediate in the synthesis of a nucleoside or analogue thereof.

[0060] In some embodiments, the present disclosure provides a method of synthesizing a nucleoside or analogue thereof, the method comprising: reacting a halogen or halogen-containing compound with an aryl- or heteroarylsubstituted compound in the presence of a catalyst compound according to Formula (I):

[0061] In some embodiments, the proline may be L-proline or D-proline. [0062] In some embodiments, the Lewis acid may be, without limitation, a halophilic Lewis acid.

[0063] In some embodiments, the Lewis acid may be, without limitation, lnCI₃ or Sc(OTf)₃.

[0064] In some embodiments, Lewis acid-promoted AHD may yield a C2',C3'-protected nucleoside or NA.

[0065] In some embodiments, Lewis acid-promoted AHD may result in protecting group migration, i.e., may yield a NA with a migrated acetonide protecting group.

[0066] In some embodiments, Lewis acid-promoted AHD may result in deprotection.

[0067] In some embodiments, the base may be, without limitation, NaOH, K₂CO₃, KHCO₃, Na₂CO₃, NaHCO₃, KOH, LiOH, Li₂CO₃, LiHCO₃, Cs₂CO₃, CsHCO₃, or CsOH.

[0068] In some embodiments, the base-promoted AHD may yield a C3’,C5’-protected NA.

[0069] In some embodiments, the aHAR reaction products may be reduced and separated prior to treatment with a Lewis base.

[0070] In some embodiments, the present disclosure provides the following nucleosides or analogues thereof, including without limitation diastereomers thereof, where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl and each R may independently be -OH, -OC(CH₃)₂O-, -(CH₂)₃-, -CH₂SCH₂-, or -CH₂OCH₂-:

[0071] In some embodiments, the present disclosure provides the following compounds, or enantiomers thereof, where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl; X may be halogen and each R may independently be -OH, -OC(CH₃)₂O-, - (CH₂)₃-, -CH₂SCH₂-, or -CH₂OCH₂-, for use as an intermediate in the synthesis of a nucleoside or analogue thereof:

[0072] In some embodiments, the present disclosure provides the following compounds, or enantiomers thereof, where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl; X may be halogen; Y may be CH₂, O, S, NR’, where R’ may be alkyl or aryl, and Z may be a protecting group for an alcohol, including without limitation, acetonide, silyl protecting group, alkyl protecting group or aryl protecting group (including cyclic or acyclic), for use as an intermediate in the synthesis of a nucleoside or analogue thereof:

[0073] In some embodiments, the present disclosure provides the following compounds, or enantiomers thereof, where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl and X may be halogen, for use as an intermediate in the synthesis of a nucleoside or analogue thereof:

[0074] In some embodiments, the present disclosure provides the following compounds, or enantiomers thereof, where NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl; X may be halogen; and Y may be CH₂, O, S, NR’, where R’ may be alkyl or aryl, for use as an intermediate in the synthesis of a nucleoside or analogue thereof:

[0075] In some embodiments, the methods disclosed herein provide rapid access to intermediates in the synthesis of nucleosides or analogues thereof in good enantioselectivity and/or yield, for example, greater than about 10g to about 400g, or any value in between, for example 10g, 15g, 20g, 25g, 50g, 75g, 100g, 125g, 150g, 200g, 250g, 300g, 350g, or 400g. Accordingly, the methods disclosed herein may be used in the process scale production of nucleosides and/or NAs.

[0076] In some embodiments, the methods disclosed herein enable direct access to C3VC5' protected NAs, where R may be alkyl, alkynyl or aryl and NB may be optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl (and hence C2' modified NAs), provide flexibility in nucleobase substitution, and/or offer a direct route to C4' modified NAs:

R = alkyl, alkynyl, aryl

C37C5' protected NA

[0077] In some embodiments, the methods disclosed herein enable direct incorporation of a wide range of nucleobases and the selective functionalization of the C2' position of the furanose core of natural nucleosides and NAs including, without limitation, C-linked or L- configured NAs.

[0078] In some embodiments, in the methods disclosed herein, replacement of the reductant with an organomagnesium reagent provides direct access to an array of C4'-modified NAs including, without limitation, locked nucleic acids (LNAs). [0079] In some embodiments, the synthesis methods disclosed herein may be useful, without limitation, in the production of D- and L-nucleosides and nucleoside analogues, locked nucleic acids, iminonucleosides, thionucleosides, C4'-modified nucleosides and/or C2'-modified nucleosides.

[0080] In some embodiments, the methods disclosed herein may be useful as a tool for drug design.

[0081] In some embodiments, the nucleoside analogues disclosed herein may be used as small molecule therapeutics or as monomers in oligonucleotide therapeutics.

[0082] In some embodiments, the methods disclosed herein may be useful in the preparation of diversity libraries. For example, larger collections of C4'-modified NAs (e.g., focused screening libraries) can be generated using the methods described herein.

[0083] By “nucleoside” is meant a glycosylamine having a nitrogenous base or “nucleobase” or “NB,” and a sugar ring (e.g., ribose or deoxyribose), in which the anomeric carbon is linked through a glycosidic bond to the N9 of a purine (e.g., adenine or guanine) or the N1 of a pyrimidine (e.g., cytosine, thymine, or uracil). Nucleosides include both L- and D- nucleoside isomers. Examples of nucleosides include cytidine, uridine, adenosine, guanosine, thymidine and inosine.

[0084] Nucleoside analogues (NAs) are compounds that are structurally similar to naturally occurring nucleosides. NAs may include, without limitation, compounds with modifications at positions C1’, C2’, C3’, C4’ and/or C5’ of the sugar ring. In some embodiments, NAs may exist as a free triol or may be phosphorylated at C3’ and/or C5’. In some embodiments, NAs may include, without limitation, compounds with a saturated or unsaturated carbocyclic ring. In some embodiments, NAs may include nitrogen or sulfur in the sugar ring, for example as a replacement for the naturally occurring oxygen, and/or may include N-R groups, where R may be without limitation alkyl, allyl, alkynyl or benzyl. In some embodiments, the nucleoside analogues disclosed herein may be modified to function as a phosphoramidate or phosphonamidate compound, e.g., a “ProTide,” which includes a 5'-nucleoside monophosphate in which the two hydroxyl groups are masked with an amino acid ester and an aryloxy component which can be enzymatically metabolized to deliver free 5'- monophosphate, which is further transformed to the active 5'-triphosphate form of the nucleoside analogue, once delivered to a cell. [0085] The “NB” or nucleobase of an NA may be any aryl or heteroaryl attached from the C1 position to a carbon or nitrogen atom. NBs may also be modified, for example, may be 5,6- dihydrouracil, 5-methylcytosine, 5-hydroxymethylcytosine, 5,5,5-trifluoromethylthymine, 5- fluorouracil, 2-thiouracil, 4-methylbenzimidazole, hypoxanthine, 7-deazaguanine, 7- deazaadenine, indole, imidazole, triazole, pyrrole, pyrazole, etc. Enantiomers of aldol products (halohydrins) can be produced using proline (e.g., L-proline or D-proline) catalysis. It is to be understood that the selection of L-proline or D-proline will depend on the stereochemistry of the catalyst compound such that the proline will be appropriately paired with the catalyst compound. For example, and solely for the purpose of illustration, in Scheme 4, when L-catalyst 1 is appropriately paired with L-proline, the stereochemistry of the resulting NA will be configured naturally while, when D-catalyst 1 is appropriately paired with D-proline, the stereochemistry of the resulting NA will be the enantiomer of the naturally- configured NA. If, however, D-catalyst 1 is paired with L-proline, the stereochemistry of the resulting NA can be unpredictable and therefore unknown.

1 ) L-catalyst 1 , NFSI

2) L-proline, dioxanone

OH OH naturally internally configured NA, natural overall sterochemistry

1 ) D-catalyst 1 , NFS I

2) D-proline, dioxanone

naturally internally configured NA, enantiomer of natural overall sterochemistry

NB

O 1 ) D-catalyst 1 , NFS I

2) L-proline, dioxanone

Non-naturally configured NA Unknown overall stereochemistry

Scheme 4 [0086] As used herein the singular forms “a”, “and”, and “the” include plural referents unless the context clearly dictates otherwise. For example, “a compound” refers to one or more of such compounds. Throughout this application, it is contemplated that the term “compound” or “compounds” refers to the compounds discussed herein and includes precursors and derivatives of the compounds. The compounds of the present invention may contain one or more asymmetric centers and can thus occur as racemates and racemic mixtures, single enantiomers, diastereomeric mixtures and individual diastereomers. Additional asymmetric centers may be present depending upon the nature of the various substituents on the molecule. Each such asymmetric center will independently produce two optical isomers and it is intended that all of the possible optical isomers and diastereomers in mixtures and as pure or partially purified compounds are included within the ambit of this invention, unless specifically indicated otherwise. Any formulas, structures or names of compounds described in this specification that do not specify a particular stereochemistry are meant to encompass any and all existing isomers as described above and mixtures thereof in any proportion. When stereochemistry is specified, the invention is meant to encompass that particular isomer in pure form or as part of a mixture with other isomers in any proportion. Single enantiomers, i.e., optically active forms, can be obtained by asymmetric synthesis or by resolution of the racemates. Resolution of the racemates can be accomplished, for example, by conventional methods such as crystallization in the presence of a resolving agent; chromatography, using, for example a chiral HPLC column; or derivatizing the racemic mixture with a resolving reagent to generate diastereomers, separating the diastereomers via chromatography, and removing the resolving agent to generate the original compound in enantiomerically enriched form. These procedures can be repeated, if desired, to increase the enantiomeric purity of a compound. When the compounds described herein contain olefmic double bonds or other centers of geometric asymmetry, and unless otherwise specified, it is intended that the compounds include the cis, trans, Z- and E- configurations. Likewise, all tautomeric forms are also intended to be included.

[0087] The starting materials can be obtained from commercial sources, prepared from commercially available organic compounds, and/or prepared using known synthetic methods.

[0088] The present invention will be further illustrated in the following examples. [0089] Examples

Materials and Methods:

[0090] Nuclear magnetic resonance (NMR) spectra were recorded using deuterochloroform (CDCI₃), deuteromethanol (CD₃OD), deuteroacetone ((CD₃)₂CO), deuteroacetonitrile (CD₃CN) or deuterodimethyl sulfoxide (DMSO-cfe) as the solvent. Signal positions (6) are given in parts per million from tetramethylsilane (6 0) and were measured relative to the signal of the solvent (¹H NMR: CDCI₃: 6 7.26; CD₃OD: 6 3.31 ; (CD₃)₂CO: 6 2.05; CD₃CN: 6 1.96; DMSO-C/₆: 6 2.50; ¹³C NMR: CDCI₃: 6 77.16; CD₃OD: 6 49.00; (CD₃)₂CO: 6 29.84; CD₃CN: 6 1.32; DMSO-cfe: 39.5). Coupling constants (J values) are given in Hertz (Hz) and are reported to the nearest 0.1 Hz. ¹H NMR spectral data are tabulated in the order: multiplicity (s, singlet; d, doublet; t, triplet; q, quartet; sept, septet; m, multiplet; br broad), coupling constants, number of protons. NMR spectra were recorded on a Bruker Avance 600 equipped with a QNP or TCI cryoprobe (600 MHz), Bruker 400 (400 MHz) or Bruker 500 (500 MHz). Diastereomeric ratios (dr) are based on analysis of crude ¹H NMR. Assignments of ¹H are based on analysis of ¹H-¹H-COSY and nOe spectra. Assignments of ¹³C are based on analysis of HSQC spectra.

Example 1 :

[0091] 1 (50mg, 0,27mmol) was stirred in acetonitrile (2.4 mL) at 4°C. Catalyst 2 ((S)-5- benzyl-2,2,3-trimethylimidazolidin-4-one-HCI) (1 eq, 59 mg, 0,27mmol), NFSI (1 eq, 23 mg, 0,27mmol) and NaHCO₃ (1 eq, 59 mg, 0,27mmol) were added, and the reaction was stirred for 48 hours. Once the starting material was completely consumed, D-proline (1 eq, 31 mg, 0,27mmol) and a solution of 2,2-dimethyl-1 ,3-dioxan-5-one (dioxanone) (0.66 eq, 23 mg, 0.18 mmol) in DMF (2 mL) were added. After 4 days, the starting material was completely consumed, and the reaction was worked up. Saturated solution of NH₄CI was added, and the aqueous phase was extracted 3 times with ethyl acetate. The combined organic phases were dried with NaSC>4, filtered, and the solvent was removed under reduced pressure. The product was purified with SiO₂ column chromatography using Ethyl acetate: Hexane (7:3) as mobile phase, affording 3 as a mixture of diastereomers 5:1 , being the syn fluorohydrin the major product.

[0092] Reduction of the ketone according to literature procedures (30) followed by chiral

HPLC analysis showed a final optical purity of 97 % ee.

[0093] 2-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1 (2H)-yl)acetaldehyde (thymine aldehyde) (10 g, 59.6 mmol) ((R)-5-benzyl-2,2,3-trimethylimidazolidin-4-one-HCI (3.8 g, 14.9 mmol, 25 mol %) and NaHCO₃ (5.02 g, 59.6 mmol) were added to a 1 L flask. 200 mL CH₃CN was added and the resulting slurry was stirred in an ice bath for 15 min. NFSI (18.8 g, 596 mmol) was then added as a solid, and the slurry was stirred at 0 °C for another 30 min. The reaction mixture was stirred overnight at 3 °C.

[0094] After the fluorination, the reaction mixture was warmed to RT, and 400 mL DCM was added, followed by L-proline (6.86 g, 59.6 mmol) and 2,2-dimethyl-1 ,3-dioxan-5-one (14 mL, 119.8 mmol). The resulting reaction mixture was stirred at RT overnight.

[0095] At this point, celite was added to the stirring reaction mixture and the solution was filtered, and the filtrate washed with CH₂CI₂. The resulting clear red solution was rotovapped to dryness, then re-dissolved in 50 mL CH₂CI₂. This solution was then dropped slowly into a 600 mL of rapidly stirring EtOAc, resulting in a precipitate. Once the addition was complete, the mixture was stirred rapidly for an additional 1 h, then filtered and concentrated to dryness. The resulting red residue was dissolved in a minimal CH₂CI₂ and applied to a silica (~160 g) column, and eluted with 75% EtOAc/Hex, collecting in 50 mL fractions. The product was collected (~18 g) and crystallized from 50 mL 10% iPrOH in toluene. The crystals were filtered and washed with ice-cold toluene to yield 8.3 g crystals. These crystallize with % an equivalent of toluene. This can be removed by dissolving the crystals in hot CH₃CN, then reconcentrating.

[0096] 3: ¹H NMR (500 MHz, CDCI₃) 6 1 .46 (s, 4H), 1 .51 (s, 3H), 1 .94 (t, J = 1 .6 Hz, 4H), 3.69 (s, 1 H), 4.12 (d, J = 17.7 Hz, 1 H), 4.33 (dd, J = 17.8, 1.5 Hz, 1 H), 4.40 (dd, J = 8.9, 1.5 Hz, 1 H), 6.66 (dd, J = 42.5, 2.0 Hz, 1 H), 7.57 (s, 1 H), 8.65 (s, 1 H).

[0097] ¹⁹F NMR (471 MHz, CDCI₃) 6 -159.88, -161.58, -169.65, -177.99.

[0098] ¹³C NMR (150 MHz, CDCI₃) 6 211.18, 163.40, 149.87, 137.09, 137.06, 110.84, 101.95, 90.82, 89.43, 71.38, 71.37, 70.63, 70.48, 66.36, 23.61 , 23.24, 12.53.

[0099] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final purity of 97 % ee,.

Example 2:

[00100] Phthalamideacetaldehyde (100 mg, 0.483 mmol) was stirred in acetonitrile

(2.4 mL) at room temperature. (S)-5-benzyl-2,2,3-trimethylimidazolidin-4-one (Catalyst 1)-HCI (1 eq, 123 mg, 0.483 mmol), NFSI (1 eq, 152 mg, 0,483 mmol) and 2,6-lutidine (1 eq, 51.7 mg, 0.483 mmol) were added, and the reaction was stirred for 48 hours. Once the starting material was completely consumed, D-proline (1 eq, 31 mg, 0.24 mmol) and a solution of 2,2-dimethyl-1 ,3-dioxan-5-one (0.66 eq, 41 .9 mg, 0.322 mmol) in DCM (1 .9 mL) were added. After 2 days, the starting material was completely consumed, and the reaction was worked up. Saturated solution of NH₄CI was added, and the aqueous phase was extracted 3 times with ethyl acetate. The combined organic phases were dried with NaSO₄, filtered, and the solvent was removed under reduced pressure. The product was purified with SiO₂ column chromatography using Ethyl acetate: Hexane (1 :1) as mobile phase, affording 7 as a mixture of diastereomers 8:1 (45% yield) , being the syn fluorohydrin the major product.

[00101] 8: ¹H NMR (600 MHz, CD₃CN) 6 1 .81 (d, J = 0.8 Hz, 3H), 2.09 (s, 3H), 4.29 (d,

J = 3.8 Hz, 1 H), 4.31 - 4.39 (m, 1 H), 4.45 (dd, J = 8.8, 5.9 Hz, 1 H), 4.55 - 4.64 (m, 2H), 5.31 (d, J = 4.2 Hz, 1 H), 5.64 (dddd, J = 1 1 .1 , 7.8, 5.9, 4.2 Hz, 1 H), 6.95 (dd, J = 48.5, 7.9 Hz, 1 H), 8.74 - 8.79 (m, 2H), 8.79 - 8.84 (m, 2H).

[00102] ¹⁹F NMR (471 MHz, CD₃CN) 6 -162.27.

[00103] ¹³C NMR (150 MHz, CD₃CN) 6 167.89, 136.10, 132.57, 124.71 , 99.16, 91.83,

90.48, 73.45, 73.40, 71.93, 71.76, 65.19, 64.56, 28.21 , 19.34.

[00104] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final optical purity of 99 % ee.

Example 3:

[00105] N-(6-oxo-9-(2-oxoethyl)-6,9-dihydro-1 H-purin-2-yl)isobutyramide hydrochloride (protected guanidine aldehyde hydrochloride) (91 .2 mg, 0.304 mmol), (R)-5-benzyl-2,2,3- trimethylimidazolidin-4-one-HCI (15.5 mg, 0.0608 mmol) and NFSI (144.5 mg, 0.456 mmol) were slurried in dimethylformamide (1 .22 mL). 2,6-lutidine (106 mL, 0.913 mmol) was added and the reaction mixture was stirred at 3 °C overnight (3 °C). After 18 hours, 2,2-dimethyl- 1 ,3-dioxan-5-one (72 mL, 0.609 mmol) was added, followed by L-proline (70.1 mg, 0.609 mmol) and acetonitrile (4.88 mL), and the reaction mixture was stirred overnight at room temperature. After 23 hours, acetonitrile was removed via rotary evaporation. Water was added, and the solution was extracted with 3 x EtOAc. The combined organic layers were washed with 2 x satd. NaCI. The organic layer was dried over MgSO₄, filtered and concentrated to afford the crude product, which was purified via flash chromatography (70% ethyl acetate : petroleum ether to obtain the product N-(9-((1 S,2R)-2-((S)-2,2,-dimethyl-5- oxo-1 ,3-dioxan-4-yl)-1-fluoro-2-hydroxyethyl)-6-oxo-6,9-dihydro-1 H-purin-2-yl)isobutyramide (38.4 mg, 0.093 mmol, 31 %, d.r. = 10:1) as a colorless foam.

[00106] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final purity of 96 % ee,

[00107] d_H (500.1 MHz, CDCI₃) 11 .99 (1 H, br. s, H-1), 8.21 (1 H, s, H-2), 8.18 (1 H, br. s, H-3), 6.50 (1 H, dd, J 46.6, 1.6 Hz, H-4), 4.50 (1 H, d, J 8.4 Hz, H-5), 4.39 (1 H, ddd, J 22.7, 8.4, 1.6 Hz, H-6), 4.31 (1 H, ABq, J 17.7 Hz, H-7), 4.14 (1 H, ABq, J 17.7 Hz, H-7), 2.62 (1 H, septet, J 6.9 Hz, H-8), 1 .54 (3H, s, H-9), 1 .48 (3H, s, H-9), 1 .29 (6H, d, J 6.9 Hz, H-10).

Example 4:

[00108] N-(9-(2-oxoethyl)-9H-purin-6-yl)benzamide (protected adenine aldehyde) (1.01 g, 3.59 mmol), (R)-5-benzyl-2,2,3-trimethylimidazolidin-4-one-HCI (91 1 mg, 3.59 mmol) and selectfluor (1 .40 g, 3.95 mmol) was placed in a round bottom flask. Acetonitrile (10 mL) was added, followed by lutidine (831 uL, 7.18 mmol). The reaction mixture was then stirred overnight at 3 °C. After 24h, L-proline (413 mg, 3.59 mmol) was added as a solid, followed by 2,2-dimethyl-1 ,3-dioxan-5-one (633 uL, 5.39 mmoL). The solution was then stirred for 48h at 3 °C. At this point, EtOAc was added, and the resulting solution was washed with 2 x satd. NaCI. The crude product was flashed on silica using an isocrat of 3 % MeOH saturated with NH3HCO3/DCM to yield the product (1 .1g, 71 % yield) as an off-white foam.

[00109] d_H (500 MHz, CDCh) 8.85 (s, 1 H), 8.70 (s, 1 H), 8.06 (m, 2H), 7.64 (m, 1 H),

7.55 (m, 2H), 6.94 (dd, J = 46, 1 .4 Hz, 1 H), 4.58 (m, 1 H), 4.35 (m, 2H), 4.15 (m, 1 H), 3.44 (s, 1 H), 1.59 (s, 3H), 1.52 (s, 3H).

[00110] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final optical purity of 99 % ee.

Example 5:

[00111] Weigh out 2-(2,4-dioxo-3,4-dihydropyrimidin-1 (2H)-yl)acetaldehyde (70 mg, 0.45 mmol, 1.0 eq), and (R)-5-benzyl-2,2,3-trimethylimidazolidin-4-one-HCI (29 mg, 0.11 mmol, 0.25 eq) in a flame-dried round bottom flask. Dissolve in 4.5 mL of 75:25 dry DMF/MeCN. Add lutidine (50 uL, 0.45 mmol, 1.0 eq) to the stirring reaction mix. Cool the reaction mix to 3°C while stirring. Add NFSI (140 mg, 0.45 mmol, 1 .0 eq) into the stirring reaction mix. Stir at 3°C for 48h. Dilute the reaction mix with additional dry DMF (3.1 mL). Add 2,2-dimethyl-1 ,3-dioxan-5-one (190 uL, 1.6 mmol, 3.0 eq) and L-proline (99 mg, 0.86 mmol, 1 .9 eq). Stir reaction at 3°C for 72h. Dilute the reaction mix with ethyl acetate (80 mL). In a separatory funnel, wash the organic solution with 1 :1 brine and saturated NaHCO₃ (aq) (4x 10 mL). Collect and dry the organic layer with anhydrous Na₂SO₄. Filter and concentrate the organic layer using a rotatory evaporator. Purify using flash column chromatography (50% ethyl acetate : hexane) to obtain an amorphous white solid (47 mg, 34% yield, 14:1 syn: anti). [001 12] 1 H NMR (500 MHz, CDCI3) 6 7.77 (d, J = 8.2 Hz, 1 H), 6.69 (dd, J = 42.3, 1 .9

Hz, 1 H), 5.79 (dd, J = 8.2, 2.3 Hz, 1 H), 4.43 (dd, J = 9.0, 1 .5 Hz, 1 H), 4.36 (dd, J = 17.8, 1 .5 Hz, 1 H), 4.19 - 4.07 (m, 2H), 1 .54 (s, 3H), 1 .49 (s, 3H).

[001 13] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final purity of 96 % ee.

Example 6:

[001 14] In a flame-dried round bottom flask, dissolve 2-(4-chloro-5-iodo-7H- pyrrolo[2,3-d]pyrimidin-7-yl)acetaldehyde (100 mg, 0.31 mmol, 1 .0 eq), and (R)-5-benzyl- 2,2,3-trimethylimidazolidin-4-one-HCI (40 mg, 0.15 mmol, 0.5 eq) in dry DMF (3.1 mL). Add 2,4,6-trimethylpyridine (41 uL, 0.31 mmol, 1.0 eq). Cool the reaction mix to 3°C while stirring. Add NFSI (101 mg, 0.32 mmol, 1 .03 eq) into the stirring reaction mix. Stir at 3°C for 6h. Add NaHCO₃ (26 mg, 0.31 mmol, 1.0 eq), 2,2-dimethyl-1 ,3-dioxan-5-one (113 uL, 0.96 mmol, 3.1 eq) and L-proline (49 mg, 0.43 mmol, 1 .4 eq). Stir reaction at 3°C for 72h. Dilute the reaction mix in ethyl acetate (40 mL). In a separatory funnel, wash the organic solution with brine (5 x 6 mL). Collect and dry the organic layer with anhydrous Na2SO4. Filter and concentrate using a rotatory evaporator. Purify using flash column chromatography (30% ethyl acetate : hexane) to obtain an amorphous white solid (74.4 mg, 51 % yield, 10:1 syn: anti,).

[001 15] 1 H NMR (500 MHz, DMSO) 6 8.74 (s, 1 H), 8.25 (s, 1 H), 6.85 (dd, J = 48.0, 6.1 Hz, 1 H), 6.39 (d, J = 6.5 Hz, 1 H), 4.75 (dtd, J = 16.8, 6.3, 4.6 Hz, 1 H), 4.31 (dd, J = 4.6, 0.9 Hz, 1 H), 3.95 - 3.92 (m, 2H), 1 .33 (s, 3H), 1 .30 (s, 3H).

[001 16] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final purity of 99 % ee, Example 7:

[001 17] To a flamed dried vial, add 2-(5-iodo-2,4-dioxo-3,4-dihydropyrimidin-1 (2H)- yl)acetaldehyde (50 mg, 0.18mmol, 1 .0 eq), and (R)-5-benzyl-2,2,3-trimethylimidazolidin-4- one-HCI (23mg, 0.09 mg, 0.5 eq), and 2,4,6-trimethylpyridine (22 mg, 0.18 mmol, 1.0 eq). Dissolve in dry DMF (1.8mL, 0.1 M), cool the reaction mix to 3°C. Add NFSI (58 mg, 0.18 mmol, 1 .0 eq) to the reaction mix. Stir reaction at 3°C for 48h. Add 2,2-dimethyl-1 ,3-dioxan-5- one (70 mg, 0.54 mmol, 3.0 eq) and L-proline (26 mg, 0.22 mmol, 1 .25 eq) to the reaction mix. Stir at 3°C for 72 hr. Dilute the reaction in ethyl acetate (40mL). In a separatory funnel, wash the organic solution with brine (10 mL x 4). Collect and dry the organic layer with anhydrous Na₂SO₄. Filter and concentrate using a rotatory evaporator. Purify using flash column chromatography (60% ethyl acetate : hexanes) to obtain product (31 mg, 9:1 syn:anti, 41 %,) as a white solid.

[001 18] 1 H NMR (500 MHz, CDCI₃) 6 8.20 (s, 1 H) 6.67 (d, J = 42.28 Hz, 1 H), 4.42 (d, J = 9.09 Hz, 1 H), 4.37 (dd, J = 17.95, 1 .51 Hz, 1 H), 4.17 (d, J =13.45 Hz, 1 H), 4.14 (m, 1 H), 1.54 (s, 3H), 1.49 (s, 3H).

[001 19] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final purity of 99 % ee,

Example 8:

[00120] Weigh out 2-(1 H-pyrazol-1 -yl)ethane-1 ,1-diol (103 mg, 0.80 mmol, 1.0 eq), (R)-5-benzyl-2,2,3-trimethylimidazolidin-4-one-HCI (51 mg, 0.20 mmol, 0.25 eq), and sodium bicarbonate (135 uL,1 .60 mmol, 2.0 eq) in a flame-dried round bottom flask. Slurry in 2.7 mL of dry MeCN. Cool the reaction mix to 3°C while stirring. Add NFSI (256 mg, 0.80 mmol, 1 .0 eq) into the stirring reaction mix. Stir at 3°C for 24h. Dilute the reaction mix with additional dry DMF (5.3 mL). Add 2,2-dimethyl-1 ,3-dioxan-5-one (94 uL, 0.80 mmol, 1 .0 eq) and L-proline (116 mg, 1 .0 mmol, 1 .25 eq). Stir reaction at 3°C for 72h. Dilute the reaction mix with ethyl acetate (50 mL). In a separatory funnel, wash the organic solution with 1 :1 brine and saturated NaHCO₃ (aq) (3 x 10 mL). Collect and dry the organic layer with anhydrous Na₂SO₄. Filter and concentrate the organic layer using a rotatory evaporator. Purify using flash column chromatography (30% ethyl acetate : hexane) to obtain an amorphous white solid (47 mg, 47% yield, 5:1 syn: anti).

[00121] 1 H NMR (400 MHz, CDCI₃) 6 7.83 (d, 2.42 1 H), 7.58 - 7.56 (m, 1 H), 6.45 (dd, J = 49.3, 3.8 Hz, 1 H), 6.32 (t, J = 2.2 Hz, 1 H), 4.52 (ddd, J = 19.0, 6.3, 3.8 Hz, 1 H), 4.27 (dd, J = 6.4, 1 .5 Hz, 1 H), 4.18 (dd, J = 17.3, 1.5 Hz, 1 H), 3.98 (d, J = 17.3 Hz, 1 H), 1.43 (s, 3H), 1.41 (s, 3H).

[00122] Reduction of the ketone according to literature procedures (30) followed by chiral HPLC analysis showed a final purity of 97 % ee.

[00123] References

1. G. M. Blackburn, Gait, M. J., Loakes, D., Williams, D. M., Ed., Nucleic Acids in Chemistry and Biology, (Royal Society of Chemistry, Cambridge, UK, 2006), pp. 503.

2. C. M. Galmarini, J. R. Mackey, C. Dumontet. Nucleoside Analogues and Nucleobases in Cancer Treatment. Lancet Oncol. 3, 415-424 (2002).

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5. D. M. Huryn, M. Okabe. AIDS-Driven Nucleoside Chemistry. Chem. Rev. 92, 1745- 1768 (1992).

6. J. Shelton et al. Metabolism, Biochemical Actions, and Chemical Synthesis of Anticancer Nucleosides, Nucleotides, and Base Analogs. Chem. Rev. 116, 14379- 14455 (2016).

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9. M. K. Yates, K. L. Seley-Radtke. The Evolution of Antiviral Nucleoside Analogues: A Review for Chemists and Non-Chemists. Part II: Complex Modifications to the Nucleoside Scaffold. Antiviral Res. 162, 5-21 (2019).

10. H. Ma etal. Characterization of the Metabolic Activation of Hepatitis C Virus Nucleoside Inhibitor Beta-D-2'-Deoxy-2'-Fluoro-2'-C-Methylcytidine (PSI-6130) and Identification of a Novel Active 5'-Triphosphate Species. J. Biol. Chem. 282, 29812-29820 (2007).

11. E. P. Gillis, K. J. Eastman, M. D. Hill, D. J. Donnelly, N. A. Meanwell. Applications of Fluorine in Medicinal Chemistry. J. Med. Chem. 58, 8315-8359 (2015).

12. J. Deval, M. H. Powdrill, C. M. D'Abramo, L. Cellai, M. Gotte. Pyrophosphorolytic Excision of Nonobligate Chain Terminators by Hepatitis C Virus NS5B Polymerase. Antimicrob. Agents Chemother. 51 , 2920-2928 (2007).

13. H. Ohrui. 2'-Deoxy-4'-C-Ethynyl-2-Fluoroadenosine, a Nucleoside Reverse Transcriptase Inhibitor, is Highly Potent Against All Human Immunodeficiency Viruses Type 1 and Has Low Toxicity. Chem. Rec. 6, 133-143 (2006).

14. J. T. Witkowski, R. K. Robins, R. W. Sidwell, L. N. Simon. Design, Synthesis, and Broad Spectrum Antiviral Activity of 1 -Beta-D-Ribofuranosyl-1 ,2,4-Triazole-3-Carboxamide and Related Nucleosides. J. Med. Chem. 15, 1150-1154 (1972). J. Zeidler, D. Baraniak, T. Ostrowski. Bioactive Nucleoside Analogues Possessing Selected Five-Membered Azaheterocyclic Bases. Eur. J. Med. Chem. 97, 409-418 (2015). G. Ni et al. Review of a-Nucleosides: From Discovery, Synthesis to Properties and Potential Applications. RSC Advances 9, 14302-14320 (2019). G. Gumina, G. Y. Song, C. K. Chu. L-Nucleosides as Chemotherapeutic Agents. FEMS Microbiol. Let. 202, 9-15 (2001). H. Cui et al. Synthesis and Evaluation of alpha-Thymidine Analogues as Novel Antimalarials. J. Med. Chem. 55, 10948-10957 (2012). Chemical Synthesis of Nucleoside Analogues. P. Merino, Ed., (John Wiley & Sons, Inc., 2013), pp. 895. M. Brodszki et al. Synthesis of the Hepatitis B Nucleoside Analogue Lagociclovir Valactate. Org. Process. Res. Dev. 15, 1027-1032 (2011). M. McLaughlin et al. Enantioselective Synthesis of 4'-Ethynyl-2-fluoro-2'- deoxyadenosine (EFdA) via Enzymatic Desymmetrization. Org. Let. 19, 926-929 (2017). W. T. Markiewicz, M. Wiewiorowski. A New Type of Silyl Protecting Groups in Nucleoside Chemistry. Nucleic Acids Res. 5, s185-s190 (1978). K. R. Campos et al. The Importance of Synthetic Chemistry in the Pharmaceutical Industry. Science 363, eaat0805 (2019). M. Peifer, R. Berger, V. W. Shurtleff, J. C. Conrad, D. W. MacMillan. A General and Enantioselective Approach to Pentoses: a Rapid Synthesis of PSI-6130, the Nucleoside Core of Sofosbuvir. J. Am. Chem. Soc. 136, 5900-5903 (2014). D. Chapdelaine et al. A stereoselective approach to nucleosides and 4'-thioanalogues from acyclic precursors. J. Am. Chem. Soc. 131 , 17242-17245 (2009). R. Britton, B. Kang. alpha-Haloaldehydes: Versatile Building Blocks for Natural Product Synthesis. Nat. Prod. Rep. 30, 227-236 (2013). W. Ren et al. Revealing the mechanism for covalent inhibition of glycoside hydrolases by carbasugars at an atomic level. Nat. Commun. 9, 3243 (2018). A. Quintard, J. Rodriguez. Bicatalyzed Three-Component Stereoselective Decarboxylative Fluoro-Aldolization for the Construction of Elongated Fluorohydrins. ACS Catalysis 7, 5513-5517 (2017). T. C. Britton, M. E. LeTourneau. (1995). Process for Anomerizing Nucleosides. US 5,420,266. Eli Lilly and Company. Meanwell et al, Science, 2020, 369, 725-730 [00124] All citations are hereby incorporated by reference.

[00125] The present invention has been described with regard to one or more embodiments. However, it will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims. Therefore, although various embodiments of the invention are disclosed herein, many adaptations and modifications may be made within the scope of the invention in accordance with the common general knowledge of those skilled in this art. Such modifications include the substitution of known equivalents for any aspect of the invention in order to achieve the same result in substantially the same way. Numeric ranges are inclusive of the numbers defining the range. In the specification, the word “comprising” is used as an open-ended term, substantially equivalent to the phrase “including, but not limited to,” and the word “comprises” has a corresponding meaning. It is to be however understood that, where the words “comprising” or “comprises,” or a variation having the same root, are used herein, variation or modification to “consisting” or “consists,” which excludes any element, step, or ingredient not specified, or to “consisting essentially of’ or “consists essentially of,” which limits to the specified materials or recited steps together with those that do not materially affect the basic and novel characteristics of the claimed invention, is also contemplated. The elements of the present invention as described may be indicated specific embodiments, however, it should be understood that they may be combined in any manner and in any number to create additional embodiments. The variously described examples and preferred embodiments should not be construed to limit the present invention to only the explicitly described embodiments. This description should be understood to support and encompass embodiments which combine the explicitly described embodiments with any number of the disclosed and/or preferred elements. Furthermore, any permutations and combinations of all described elements in this application should be considered disclosed by the description of the present application unless the context indicates otherwise. Citation of references herein shall not be construed as an admission that such references are prior art to the present invention. All publications are incorporated herein by reference as if each individual publication was specifically and individually indicated to be incorporated by reference herein and as though fully set forth herein. The invention includes all embodiments and variations substantially as hereinbefore described and with reference to the examples.

Claims

WHAT IS CLAIMED IS:

1. A method of synthesizing a haloaldehyde compound, the method comprising reacting a halogen or halogen-containing compound with an aryl- or heteroarylsubstituted compound in the presence of a catalyst compound according to Formula I:

Formula (I) wherein

Ri, R2, R3, and R₄ are each independently H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and

Cx is a salt counterion, to yield the haloaldehyde compound.

2. A method of preparing an intermediate in the synthesis of a nucleoside or analogue thereof, the method comprising: i) reacting a halogen or halogen-containing compound with an aryl- or heteroaryl-substituted compound in the presence of a catalyst compound according to Formula I:

Formula (I) wherein

R1, R2, R3, and R₄ are each independently H, alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, or acyl; and

Cx is a salt counterion, to yield a haloaldehyde compound; ii) performing an enantioselective aldol reaction by proline catalysis to yield a halohydrin compound, to yield an intermediate in the synthesis of a nucleoside or analogue thereof.

3. The method of claim 2, further comprising reducing the halohydrin compound to obtain a halohydrin diol compound.

4. A method of synthesizing a nucleoside or analogue thereof, the method comprising:

(i) reacting a halogen or halogen-containing compound with an aryl- or heteroaryl-substituted compound in the presence of a catalyst compound according to Formula I:

Formula (I) wherein

Cx is a salt counterion, to yield a haloaldehyde compound; iii) performing an enantioselective aldol reaction by proline catalysis to yield a halohydrin compound; iv) reducing the halohydrin compound to yield a halohydrin diol compound; and v) contacting the halohydrin diol compound with a Lewis acid or a base in an annulative halide displacement (AHD) reaction, to yield a nucleoside or analogue thereof.

5. The method of any one of claims 1 to 4, wherein the halogenation is enantioselective.

6. The method of any one of claims 2 to 5 wherein the proline is L-proline or D- proline.

7. The method of any one of claims 4 or 6 wherein the Lewis acid is a halophilic Lewis acid.

8. The method of any one of claims 4 or 7 wherein the Lewis acid is I nCI₃ or Sc(OTf)₃.

9. The method of any one of claims 4 to 8 wherein the Lewis acid-promoted AHD yields a C2',C3'-protected nucleoside or analogue thereof, a nucleoside or analogue thereof with a migrated acetonide protecting group, or results in deprotection.

10. The method of any one of claims 3 to 9 wherein the halohydrin diol compound is separated prior to treatment with the base.

11 . The method of claim 4, 5, 6 or 9 wherein the base is NaOH, K₂CO₃, KHCO₃, Na₂CO₃, NaHCO₃, KOH, LiOH, Li₂CO₃, LiHCO₃, Cs₂CO₃, CsHCO₃, or CsOH.

12. The method of claim 4, 5, 10 or 11 wherein the base-promoted AHD yields a C3’,C5’-protected nucleoside or analogue thereof.

13. The method of any one of claims 2 to 12 wherein the halohydrin compound is:

wherein NB is optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl, and X is a halogen.

14. The method of any one of claims 2 to 13 wherein the halohydrin compound is:

15. The method of any one of claims 3 to 14 wherein the halohydrin diol compound is:

16. The method of any one of claims 1 to 15 wherein the halogen is fluorine, bromine, chlorine, or iodine.

17. The method of any one of claims 1 to 15 wherein the halogen-containing compound is an electrophilic halogenating agent.

18. The method of any one of claims 1 to 15 wherein the halogen-containing compound is N-Fluorobenzenesulfonimide (NFSI), Selectfluor™, Xtalfluor™, N- halosuccinimide, N-chlorinated hydantoin, Palau’chlor™, or N-fluoropyridinium.

19. The method any one of claims 1 to 18 wherein the salt counterion is HCI, TFA, HBr, or MsOH.

20. The method of any one of claims 1 to 19 wherein the catalyst compound is

21 . The method of any one of claims 1 to 19 wherein the aryl- or heteroaryl- substituted compound comprises the following chemical structure:

or

wherein NB is optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl.

22. The method of any one of claims 1 to 21 wherein the haloaldehyde compound comprises the following chemical structure:

H' '³

X wherein NB is optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl,

X is a halogen, and

* refers to enantioenrichment.

23. The method of any one of claims 1 to 22 wherein the haloaldehyde compound is:

24. The method of any one of claims 4 to 23 wherein the nucleoside or analogue thereof is:

, or wherein NB is optionally substituted aryl, arylalkyl, heteroaryl, or heteroarylalkyl and each R is independently -OH, -OC(CH₃)₂O-, -(CH₂)3-, -CH₂SCH₂-, or - CH₂OCH₂-.

25. The method of any one of claims 4 to 24 wherein the nucleoside or analogue thereof is a C3VC5' protected NA, a C4' modified NA, a C2' modified NA, a C- linked NA, a L-configured NA, a D- nucleoside or analogue thereof, a L- nucleoside or analogue thereof, a locked nucleic acid, an iminonucleoside, or a thionucleoside.

26. A halohydrin compound that is: