WO2011117324A2

WO2011117324A2 - Process for the preparation of vitamin k2

Info

Publication number: WO2011117324A2
Application number: PCT/EP2011/054499
Authority: WO
Inventors: Lars SKATTEBØL; Inger Reidun Aukrust; Marcel Sandberg
Original assignee: Kappa Bioscience As
Priority date: 2010-03-23
Filing date: 2011-03-23
Publication date: 2011-09-29
Also published as: WO2011117324A3; GB201004876D0

Abstract

A new process for making polyprenols is described as well as the use of these building blocks in the synthesis of Vitamin K2. The process involves reaction of a compound of formula (X) with a compound of formula (XI) in the presence of a base so as to form a compound of formula (XII) and conversion of that compound into a compound of formula (XIII).

Description

Process for the preparation of vitamin K2

This application relates to a process for the synthesis of a key intermediate in the manufacture of vitamin K2, as well as the synthesis of vitamin K2 itself. The key intermediate forms a further aspect of the invention.

Vitamin K denotes a group of lipophilic and hydrophobic vitamins that are needed for the post-translational modification of certain proteins, mostly required for blood coagulation. Chemically they are 2-methyl-l,4-naphthoquinone derivatives.

Vitamin K is not a single compound, rather it is a series of related homologues. Vitamin Kl is called phylloquinone and has the systematic name all- E-2-methyl-3-(3,7, 11 , 15-tetramethylhexadec-2-enyl)naphthalene- 1 ,4-dione. Vitamin K2 (menaquinone) is normally produced by bacteria in the intestines, and dietary deficiency is extremely rare unless the intestines are heavily damaged or are unable to absorb the molecule.

Vitamin K2 is a mixture of different molecules based on a naphthoquinone structure and varying lengths of isoprenoid chains. The compound MK-7 (i.e. 7 isoprenyl groups) is depicted below but other components of the vitamin have different numbers of isoprenoid links. Menaquinones have side chains composed of all-E polyprenyl residues; generally they are designated as MK-n, where n specifies the number of isoprenoid repeating units. The minimum value of n is 2.

All members of the vitamin K group of vitamins share a methylated naphthoquinone ring structure, and vary in the aliphatic side chain attached at the 3- position. It is generally accepted that the naphthoquinone is the main functional group of the vitamin, so that the mechanism of action is similar for all K-vitamins.

Substantial differences may be expected, however, with respect to intestinal absorption, transport, tissue distribution, and bio-availability when variations in the side chain take place. These differences are caused by the different lipophilicity of the various side chains and by the different food matrices in which they occur.

A recent paper (Suhara et al., Biorganic Med. Chem Lett. 17 (2007) 1622- 1625) suggests the use of certain vitamin K metabolites as biologically active compound which can lead to the development of new drugs based on side-chain modification of the alkyl group. Suhara targets compounds of structure similar to metabolites of vitamin K, i.e. compounds carrying acidic (or other strongly hydrophilic groups) at the terminus of the 3 -position side chain. Some of the analogues have apoptosis-inducing properties.

It is known that γ-carboxylated osteocalcin is involved in the bone remodeling system, and there are strong indications that vitamin K has a beneficial effect on bone diseases such as osteoporosis. There is interest therefore in the investigation of various vitamin K2 type compounds for inhibitory effects on osteoporosis, as potential anti-cancer drugs and for beneficial cardio-vascular activity.

Whilst vitamin K2 occurs naturally in various vegetables and can be produced by bacteria in the intestines, it is still an interesting synthetic target as isolation of the vitamin from a natural source is complex and concentrations of the vitamin are low. Moreover, synthesis allows the preparation of particular menaquinones rather than the isolation of a mixture of different menaquinones.

Various individuals have synthesized the menaquinone compounds which form part of vitamin K2 or components thereof. The first synthesis of

menaquinones, reported by Isler et al, Helv. Chim Acta 1958, 41, 786-807, used a nonstereospecific approach. Tso and Chen , J Chem Res 1995, 104-105 describes a one pot synthesis of vitamin K although he concentrates on the formation of the naphthoquinone ring as opposed to the side chain of the molecule. His chemistry involves the reaction of 3 -substituted isobenzofuranones with vinylic sulphones to form the naphthoquinone ring structure. Suhara et al, Bioorg Med Chem Lett 17, (2007) 1622-1625, describe various syntheses of menaquinone analogues in which the terminal methyl group is converted to a hydroxyl, aldehyde or acid group.

Naruta, J Org Chem 1980, 45, 4097-4104, describes the synthesis of some vitamin K2 analogues using trialkylallylstannane chemistry to bond the preformed side-chain to the naphthoquinone group.

The present inventors have devised a synthetic strategy for the formation of MK-7 and other menaquinones involving the synthesis of a key intermediate in the manufacturing process. The successful synthesis of MK-7 and other menaquinones relies on the formation of polyprenols, i.e. chains of repeating isoprenoid units. The present inventors have devised a new synthetic strategy for forming polyprenols and have utilized this methodology in the manufacture of vitamin K2 itself.

Thus, viewed from one aspect the invention provides a process comprising reacting a compound of formula (X)

wherein Y is S0₂Ar or SAr;

Ar is a C6-10 aryl group or C7-12 arylalkyl group;

p is 0 to 4;

with a compound of formula (XI)

wherein Ri is a hydroxyl protecting group such as Ci_₆ alkyl ester protecting group, especially acetate;

LG is a leaving group such as halo; and

q is 0 to 4;

in the presence of a base so as to form a compound of formula XII

(XII)

and converting said compound into a compound of formula XIII

e.g. by reduction such as using a lithium based reducing agent such as LiHBEt₃.

The key intermediate (XII) in the formation the polyprenol (XIII) and hence in the formation of vitamin K2, also forms a further aspect of the invention. Thus, viewed from another aspect the invention also provides a compound of formula (XII)

wherein R_ls Y, p and q are as hereinbefore defined.

It is particularly preferred if the key intermediate is a compound of formula

(XIV)

The process of the invention allows therefore the formation of polyprenols and hence menaquinones in high yield and crucially with stereochemical integrity. In particular, the inventors do not see any presence of Z-isomers during their reactions.

The polyprenols which are formed by this process can be manipulated in various ways to ensure the formation of various menaquinone products.

For example, these intermediates can be used in conjunction with Kumada or Suzuki chemistry to connect a side chain to the naphthoquinone ring of vitamin K2. This chemistry is explained in detail below.

KUMADA

The use of Kumada chemistry to bind an isoprenoid side chain to the naphthoquinone ring involves a process for the preparation of a compound of formula (I)

This can be achieved using a step in which (i) a compound of formula (II) is reacted with a compound of formula (III)

wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; LG is a leaving group;

m is an integer of from 0 to 8;

n is an integer of from 0 to 9;

in the presence of a copper, nickel or palladium catalyst.

The compound of formula (III) is obviously readily derived from a compound of formula (XIII) above simply by converting the OH group into a leaving group. The skilled man can devise numerous ways of converting a hydroxyl group into a leaving group. For example, the OH group can be converted into a halide using PBr₃.

SUZUKI

Alternatively, Suzuki chemistry provides a process for the preparation of a compound of formula (I)

wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; is reacted with a compound of formula (III)

wherein LG is a leaving group, m is an integer of from 0 to 8, n is 0 to 9; in the presence of a Pd (0) catalyst.

The compound of formula (III) is obviously readily derived from a compound of formula (XIII) above.

The combination therefore of the process for the formation of a compound of formula (XIII), conversion thereof to compound (III) and subsequent Kumada or Suzuki chemistry as noted above forms a further aspect of the invention. Biellmann

Thus, the successful use of either Kumada or Suzuki coupling for preparing the vitamin K2 compounds depends on the availability of a precursor for the all-E polyprenyl side chains. To reach this objective the inventors have employed Biellmann type chemistry as hereinbefore defined. This reaction involves the formation of an arylthio or arylsulfonyl substituted compounds and reaction of these sulphur compounds with an electrophile, such as a halide, in the presence of a base. Crucially, the electrophile also carries a protected OH group (see formula XI).

Preferably the Ar group is napthyl, xylyl, tolyl or phenyl. Most especially it is phenyl and throughout the discussion which follows reference is typically made to phenylthio or phenylsulphonyl although of course other Ar groups than Ph can be employed and this language should not be regarded as limiting.

It is preferred if p and q are 0 to 2, especially 1 or 2. It is especially preferred if p is not 0, e.g. 1-4, or 1-3 or most preferably 1 to 2. It is especially preferred if q is not 0, e.g. 1-4, or 1-3 or most preferably 1 to 2.

Suitable bases for allowing the reaction of compounds (X) and (XI) are n- butyl lithium, tert butyl lithium, and other non nucleophilic bases such as tertbutoxides.

After coupling, the phenylthio or phenylsulfonyl groups are removed reductively. It is an important feature of the invention that this reduction step can be effected in the absence of a metal reducing agent such as Li metal. Any reducing agent which is capable of reducing the -S0₂ or -S- group to H may be used here. It is also preferred if the reducing agent also removes the protecting group to leave -OH. Suitable reducing agents include lithium aluminium hydride, LiHBEt₃, and sodium borohydride. It is preferred if the reducing step also reduces the protecting group to an alcohol to leave a polyprenol compound.

The inventors have found that this method is ideal for coupling together two isoprenoid chains to make a new isoprenoid chain of, for example, 5 or more units.

The formed coupling compound of formula (XIII) is ideally a pentaprenol. Thus, it is preferred if in compounds (X) and (XI) one of p and q is one and the other is 2.

It will be appreciated that the value of m and n in the compounds discussed herein are related also to the values of p and q.

The process of the invention may therefore incorporate further steps after the claimed reaction as described below in order to allow the formation of a compound of formula (I), especially MK-7.

For example, the reaction of compounds (II) and (III) or (IV) and (III) yields the compound (Γ):

It will be appreciated that to complete the synthesis of a compound of formula (I) it is necessary to convert the diprotected naphthoquinone (Γ) back to naphthoquinone. This can be achieved by any convenient oxidation method although typically cerium ammonium nitrate (CAN) can be used.

Definitions:

A polyprenyl side chain is one which derives from the polymerisation of isoprene: 2-methyl- 1 ,3-butadiene. Unless otherwise stated, an alkyl group can contain 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, especially methyl or ethyl. In all embodiments R is preferably methyl.

Halide (Hal) includes fluoro, chloro, bromo and iodo, preferably chloro or bromo. Halides employed as Grignard reagents are preferably bromo.

The term leaving group is well known in the art and denotes an atom or group of atoms that readily leaves a molecule due to the relative stability of the ion formed. Useful leaving groups include halides, tosylates, mesylates and triflates. In any embodiment of the invention, preferred leaving groups are halides.

In any embodiment of the invention "n" is preferably 0 to 9, preferably 1 to

8, more preferably 4 to 7, e.g. 6, 7 or 8 isoprenoid units. In some embodiments n may range from 0 to 10 or 0 to 11. Ideally n is selected so that the side chain contains 7 repeating units.

In any embodiment of the invention "m"' is 0 to 8, e.g. 0 to 7, preferably 0 to 5, more preferably 1 to 4, e.g. 2, 3 or 4 isoprenoid units (unless otherwise stated). It will be appreciated that the sum of the various m and m' values of the starting materials will add up to the value of n in the compound of formula (I) taking into account any units formed in the reactions in question. Thus if one isoprene unit is formed by the reactions then n-1 is the total of all m's. Thus, the value of n reflects the values of m and m' in the reactants. Where a reaction process involves multiple reactants in which the variable m is present, it will be appreciated that each m can be different.

In any embodiment m' is preferably 0, 1 or 2, especially 0.

Any hydroxyl protecting group can be used as Ri. The use of hydroxyl protection is well known in the art. Suitable protecting groups include esters, alkylsilyl protecting groups such as trimethylSi, tertbutyldimethylSi, - butyldimethylsilyloxymethyl (TOM), and triisopropylsilyl (TIPS) ethers, benzyl, β- methoxyethoxymethyl ether (MEM), dimethoxytrityl [bis-(4- methoxyphenyl)phenylmethyl, DMT, methoxymethyl ether (MOM), methoxytrityl [(4-methoxyphenyl)diphenylmethyl, MMT), p-Methoxybenzyl ether (PMB), methylthiomethyl ether, pivaloyl (Piv), tetrahydropyranyl (THP), trityl

(triphenylmethyl, Tr), tert), methyl ethers and ethoxyethyl ethers (EE). Ri hydroxyl protecting groups of particular interest in this invention are preferably those which are reduced during the reduction of the S0₂Ar or SAr group. Preferably, the Ri group is an ester protecting group such as an alkyl ester or a benzoic ester, e.g. acetic ester or pivalic ester. The appreciation that the protecting group can be removed in the reduction step is an important advance as it shortens the synthesis of the desired polyprenol.

Detailed Description of the Invention This invention primarily relates to the synthesis of prenol building blocks which can then be used in the synthesis of vitamin K2 and in particular MK-7. Compounds of formula (I), i.e. menaquinone derivatives having varying lengths of a polyprenyl side chain in their backbone are known desirable compounds and it is preferred if there are at least 6 isoprenoid units, more preferably at least 7 isoprenoid units in the compound of formula (I). It is preferred therefore if n is at least 3, preferably 4, 5 or 6.

The compound of formula (III) required to effect some of the reactions above can contain different numbers of isoprenoid units. The compound of formula (III) is typically not commercially available and itself needs to be synthesized from compounds with a smaller number of isoprenoid units. A particular challenge faced by the synthetic chemist is preparing menaquinone compounds having different numbers of isoprenoid units thereby ensuring the E configuration of all the double bonds.

The inventors have found that Biellmann chemistry provides an ideal way to make vitamin K2 side chain molecules which can then be coupled to a

naphthoquinone ring following the chemistry described above. Alternatively this chemistry can be used to increase the size of a side chain already attached to the naphthoquinone ring following chemistry described in more detail in the passages which follow.

The most common starting materials for the formation of the isoprenoid units of formula (III) are polyprenols. The processes described above enable the formation of all kinds of polyprenols. In order to carry out the claimed process, we need to prepare a compound of formula (X) and a compound of formula (XI). Short chain polyprenols are synthetically available materials. It is possible to convert the alcohol into an alkyl ester using well known chemistry. A leaving group can then be introduced at the other end of the molecule, e.g. by introducing a hydroxyl group using selenium dioxide and conversion of that hydroxyl group into a leaving group such as halo, tosyl, mesylate and so on. Compounds of formula (XI) are therefore readily available starting materials.

The arylthio or arylsulfonyl reactant compound (X) can be made from, for example, geranylgeraniol by conversion of the alcohol to a leaving group and reaction of that leaving group with a phenylthio or phenylsulfonyl ion.

The arylthio or arylsulfonyl substituted compounds are readily deprotonated with base forming the corresponding anions which can be reacted with a compound of formula (XI) yielding the basis of the isoprenoid carbon chain. Suitable bases include tBuOK, LDA and BuLi. Preferred esters are acetates.

Scheme 1 exemplifies this type of reaction:

Scheme 1

8

The reduction of the arylthio or arylsulfonyl to the polyprenol is preferably effected using a reducing agent which is preferably not a metal. This polyprenol can be manipulated in all manner of ways in order to make menaquinones.

For example, to complete the synthesis, the naphthoquinone group must be introduced. This compound can be prepared from commercially available 2- methylnaphthoquinone as starting material as outlined in scheme 2. This brominated intermediate is converted to its dimethoxy analogue using tin dichloride in ethanol and subsequent treatment with dimethylsulphate and base. This dimethoxy derivative can then form the corresponding Grignard reagent. This chemistry is well established (Snyder and Rapoport, J Am Chem. Soc 1974, 96, 8046-8054) .

Scheme 2

Scheme 1 depicts the formation of pentaprenol but other compounds such as heptaprenol are formed analogously. It will also be appreciated that the process of the invention can be repeated to generate even longer polyprenols. As our process yields a polyprenol, this is effectively a precursor to reactants (X) and (XI) so a shorter chain polyprenol made by the process of the invention can then form the basis for a second reaction.

Heptaprenol formed by the process of the invention can be converted to a halide, but the subsequent coupling to the naphthoquinone derivative using a classical Grignard reaction is not a useful alternative. It is highly preferred if the reaction of the naphthoquinone derivative with the isoprenyl side chain is effected by Kumada coupling chemistry, as described above. The inventors have found that Kumada chemistry improves yields and again prevents any loss of stereochemistry during the formation of the menaquinone. The coupling proceeds smoothly and a menaquinone was obtained after oxidation of the methoxy groups on the naphthoquinone ring by cerium ammonium nitrate (CAN) or other oxidation methods (scheme 3).

Scheme 3

The catalyst used in the Kumada coupling can be, for example, a Cu (II), Ni (II) or Pd(0) species. Suitable compounds include nickel chloride with two dppe ligands (NiCl2(l,2-bis(diphenylphosphino)ethane)2), nickel(II) acetylacetonate and tetrakis(triphenylphosphine)palladium(0). For a detailed discussion of Kumada chemistry see Yamamura, M., Moritani, I. and Murahashi, S-I. Journal of

Organometallic Chemistry, 91 (2), 1975, C39-C42.

In another strategy leading to MK-7 the Kumada coupling is actually used twice as outlined in scheme 4. In the first Kumada coupling the Grignard reagent reacts with commercially available geranyl chloride providing the geranyl substituted derivative. Oxidation with Se0₂ affords the alcohol which is transformed into the bromide. The second Kumada coupling between this bromide and the Grignard reagent from pentaisoprenyl compound (derived from the pentaprenol of scheme 1) completed the synthesis of MK-7.

Scheme 4

The inventors also envisage the use of Suzuki coupling chemistry to effect the menaquinone synthesis. The Suzuki reaction, involves the reaction of an aryl- or vinyl-boronic acid with an aryl- or vinyl-halide catalyzed by a palladium(O) complex. In the menaquinone synthesis therefore the naphthoquinone bromide

can be converted into a boronic acid using known techniques, e.g. by

transmetallation with lithium. Once formed this boronic acid can be coupled with a suitable halide, triflate or tosylate under Suzuki conditions, i.e. using Pd(0) catalysis. The palladium catalyst is preferably 4-coordinate, and usually involves phosphine supporting groups, e.g. tetrakis(triphenylphosphine)palladium(0). Scheme 5 shows the Suzuki coupling in action. Again, the final step involves a pentaprenol derivative derivable for our process. For a more detailed discussion of Suzuki chemistry see Suzuki, A. Pure Appl. Chem. 1991, 63, 419-422. Scheme 5

In scheme 5, Suzuki chemistry is used in the formation of the MK-7 compound. Moreover, both schemes 4 and 5 introduce an alternative method of forming the menaquinone side chain, i.e. by building it up actually on the naphthoquinone structure rather than preforming the entire side chain.

It is a feature of the invention therefore that Kumada or Suzuki coupling reaction can yield only a relatively short side chain which can then be built up to form a compound of formula (I). To complete the synthesis of a longer chain menaquinone further Kumada, Suzuki or any other chemistry can be used.

Viewed from another aspect therefore the invention further comprises a process for the preparation of a compound of formula (I)

where n is m + 2; comprising

(i) reacting a compound of formula (X):

wherein Y is S0₂Ar or SAr;

Ar is a C6-10 aryl group or C7-12 arylalkyl group;

p is 0 to 4;

with a com ound of formula (XI)

LG is a leaving group such as halo; and

q is 0 to 4;

in the resence of a base so as to form a compound of formula XII

converting said compound into a compound of formula XIII

converting the compound of formula (XIII) into a compound of formula

wherein LG is a leaving group and m is the sum of p + q;

reacting said compound of formula (III) with a compound of formula

wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; in the presence of a copper, nickel or palladium catalyst; and

(v) converting the diprotected naphthoquinone into a naphthoquinone.

The reaction of a compound of formula (III) with a compound of formula (II) or (IV) in which R is not an alkyl group in the presence of a copper, nickel or palladium catalyst; and converting the diprotected naphthoquinone into a

naphthoquinone is a further aspect of the invention.

Highly preferred intermediates of this invention include

wherein R and Y are as hereinbefore defined (preferably wherein R is not methyl and/or Y is not S0₂Ph.

Ideally, the invention further comprises a process for the preparation of a compound of formula (I)

where n is m + m' +2;

comprising steps (i) to (ii) as hereinbefore defined so as to form compound

( iii); iii) converting said compound of formula (XIII) to one of formula (VII) or (VIII)

(VII)

wherein m is p+q;

(iv) reacting said compound of formula (VII) or (VIII) with a compound of formula ( )

wherein m' is 0 to 8 and X represents a leaving group;

in the presence of a Ni, Cu or Pd catalyst; and

(v) converting the diprotected naphthoquinone into a naphthoquinone.

The catalyst used here is chosen depending on the reaction in question, e.g. Pd(0) for a Suzuki coupling, Cu(II), Ni (II) or Pd(0) for Kumada. Viewed from another aspect therefore the invention further comprises a process for the preparation of a compound of formula (I)

where n is m + m' + 2;

comprising steps (i) to (ii) as hereinbefore defined to form compound (XIII);

(iii) converting said compound of formula (XIII) to one of formula (V) or

wherein m' is 0 to 8 and X represents a leaving group in the presence of a base; (v) reductively removing the arylthio or arylsulfonyl groups in the resulting compound; and

(vi) converting by oxidation the diprotected naphthoquinone into a

naphthoquinone.

Viewed from another aspect the invention provides a process for the preparation of a compound of formula (I)

where n is m + m' + 2;

comprising (i) reacting a compound of formula (V) or (VI):

wherein m is 1 to 5 and Ar is a C6-10 aryl group or C7-12 arylalkyl group (e.g. not phenyl);

with a compound of formula (Γ)

wherein m' is 0 to 8, e.g. 0, and X represents a leaving group;

in the presence of a base;

(ii) reductively removing the arylthio or arylsulfonyl groups in the resulting compounds; and

(iii) converting by oxidation the diprotected naphthoquinone into a

naphthoquinone.

By varying the number of isoprene units in either molecule coupled using the Biellmann reaction, Suzuki coupling or Kumada coupling all manner of different menaquinone compounds can be produced. It will be appreciated therefore that the values of p, q, m and m' in the reactants must be selected to match the number of repeating units desired in the compound of formula (I) bearing in mind, of course, that some isoprenoid units are formed during the reactions themselves. This will be readily achieved by the skilled man.

Ideally, MK-7 is produced especially where 2 units come from compound (III) or formula (Γ), 4 units from compound (V) or (VI) or (VII) or (VIII) (the 7th being formed by the reaction). This is the most preferred process of the invention. It is preferred therefore if m' is 0 or 1 especially 0. It is preferred if m is 2 to 4, especially 3. The preferred process is therefore

wherein any leaving group may be substituted for Br (e.g. other halogens, tosylate, mesylate etc), other protecting groups used on the naphthoquinone and any ArS0₂- or ArS group used. The 2^nd reactant can derive from our scheme 1 type synthesis. A benefit of preparing MK-7 using this "2+5" strategy is that the selenium dioxide reduction step used to form the napthoquinone reactant takes place more readily on a naphthoquinone carrying on 2 isoprenoid units than on a longer chain molecule. This "2+5" method also gives better stereochemistry and has been found to allow the formation of solid, in particular crystalline MK-7.

The inventors have also found however, that the Biellmann reaction can be carried out on a molecule in which the naphthoquinone ring (or a protected analogue thereof) is present. It may be therefore that the phenylthioether required in the Biellmann reaction already carries a naphthoquinone group.

Thus, viewed from a further aspect the invention provides a process for the preparation of a compound of formula (I) as hereinbefore defined

where n is m + m' + 2;

comprising (i) reacting a compound of formula (X):

wherein Y is S0₂Ar or SAr;

Ar is a C6-10 aryl group or C7-12 arylalkyl group; p is 0 to 4;

with a compound of formula (XI)

wherein Ri is a protecting group such as acetate;

LG is a leaving group such as halo; and

q is 0 to 4;

in the resence of a base so as to form a compound of formula XII

converting said compound into a compound of formula XIII

converting said compound of formula (XIII) to one of formula (III)

wherein m represents the sum of p + q and LG is a leaving group; reacting with a compound of formula (IX) in the presence of a base;

wherein m' is 0 to 8 and Ar is as hereinbefore defined;

(v) reductively removing the arylthio or arylsulfonyl groups; and

(vi) converting by oxidation the diprotected naphthoquinone into a naphthoquinone.

The reaction of a compound of formula (III) with a compound of formula

(IX) with subsequent reduction and oxidation to form formula (I) forms a further aspect of the invention, e.g. when R is other than alkyl.

It will be appreciated in all these processes that the values of p and q (and hence m) and the value of m' when added together (and taking into account any isoprenoid units formed during the reaction) will match the values of n.

By varying the number of isoprenoid units in either molecule coupled using the Biellmann reaction, Suzuki coupling or Kumada coupling all manner of different menaquinone compounds can be produced.

The inventors have also devised alternative routes to compounds useful in such Biellman coupling reactions to form higher menaquinones. The inventors have devised an alternative process for the manufacture of these compounds in which the naphthoquinone ring is itself synthesised. The chemistry is based on that described by Tso et al in J Chem Res 1995, 104-105. The technique involves the reaction of a isoprenyl derivative in which the hydroxyl group is converted to an appropriate leaving group such as tosylate and reacted with CH₂CHCH₂S0₂Ph in base. The base deprotonates the CH₂CHCH₂S0₂Ph compound alpha to the sulphur and this can act as a nucleophile.

This can then be reacted with the benzolactone shown below to form the methylated naphthoquinone ring structure.

Scheme 6

Treatment of this compound with selenium dioxide adds a terminal hydroxyl group which can be converted to a halide and then partake in further chemistry, e.g. in a Kumada type coupling to add further isoprenoid units to the side chain.

Thus viewed from a sixth aspect the invention provides a process for the preparation of a compound of formula (I) wherein

where n reflects the values of m;

comprising (i) reactin a compound of formula (X):

wherein Y is S0₂Ar or SAr;

Ar is a C6-10 aryl group or C7-12 arylalkyl group;

p is 0 to 4;

with a com ound of formula (XI)

wherein Ri is a protecting group such as an acetate;

LG is a leaving group such as halo; and

q is 0 to 4;

in the resence of a base so as to form a compound of formula XII

converting said compound into a compound of formula XIII

e.g. by reduction such as using a lithium based reducing agent such as LiHBEt₃;

wherein m is p+q+1 and Y is S0₂Ar or SAr where Ar is as hereinbefore defined; (iv) reacting with a compound

where Ar is as hereinbefore defined in the presence of a base;

(v) reductively removing the arylthio or arylsulfonyl groups; and

(vi) converting by oxidation the diprotected naphthoquinone into a naphthoquinone

Throughout the processes above, it may be necessary to use different solvents, coreactants and controlled reaction conditions. This is all well within the skills of the artisan. Typical solvents of use in the processes of the invention include, THF, DCM, DMSO, ethyl acetate, alcohols, amines, ethers, hydrocarbons, aryl solvents and so on. Where reactions need to be cooled, ice baths, dry ice baths or cooling machines can be used, for example. The examples which follow provide guidance on the conditions and coreactants required to effect the claimed processes.

The final products of the formula (I) formed by the processes of the invention are generally known compounds and have well documented therapeutic applications. The formed compounds may therefore be formulated as

pharmaceutically acceptable compositions. The compounds of formula (I) have utility in the treatment of osteoporosis, cancer or cardio-vascular diseases such as atherosclerosis. The compounds may also be used as vitamin supplements or in any other known application of vitamin K, e.g. for injection into new-born infants to aid blood clotting.

It is a particular feature of the invention that the MK products achieved are highly pure. They have excellent stereochemical integrity and can be manufactured as solids as opposed to oils. In particular, the MK-n compounds manufactured according to the invention can be crystalline, especially crystalline MK-7.

In the schemes above, specific reaction conditions and reagents are disclosed to aid the skilled man in carrying out the reactions claimed. The chemistry could however be carried out under different conditions and using various reagents and the skilled man is aware of this. The reactions disclosed in the schemes are therefore disclosed per se and should not be considered as being limited to the use of the particular reagents mentioned in those schemes. The reactions in the schemes are disclosed irrespective of how each reaction is accomplished as well as in conjunction with the specific reagents mentioned.

The invention will now be further described with reference to the following non limiting examples:

Scheme 7 Summaries the reactions in the examples which follow:

HC Ac₂0, DCM AcO Se0₂, fBuOOH

DMAP salisylic acid, DCM

Geraniol 97%

Farnesol

Example 1

A solution of geraniol (10.8 g, 70 mmol) in DCM (40 mL) under nitrogen was added acetic anhydride (13.2 mL, 140 mmol). Catalytic DMAP (428 mg, 3.5 mmol) was added and the mixture was stirred at room temperature for 1 hour. MeOH (20 mL) was added and the solution was stirred for another hour. Heptane (300 mL) was added and the mixture was washed with water (x2) and saturated NaHCC>3, dried (Na₂S0₄), filtered and evaporated in vacuo to afford 13.3 g (97%) of the product.

Example 2

Se0₂, t-BuOOH

salisylic acid, DCM AcC

A solution of salisylic acid (485 mg, 3.5 mmol), Se0₂ (117 mg, 1.05 mmol) and t- BuOOH (12.5 mL, 70 wt% in water, 87.5 mmol) was stirred at room temperature for 15 minutes. Geraniol acetate (6.86 g, 35.0 mmol) was added and the mixture was stirred at room temperature for 2 nights (1 night is probably enough). The mixture was concentrated in vacuo (T<30°C). Diethyl ether (50 mL) was added and the mixture was washed with 3 M NaOH (3x10 mL, aq), water (3x10 mL) and brine (10 mL). The organic phase was dried (Na₂S0₄), filtered and concentrated in vacuo. Flash chromatography (silica, heptane:EtOAc 80:20, 75:25) afforded 2.4 g (33%) of the product. Example 3

A solution of the alcohol (7.43 g, 35 mmol) in THF (120 mL) was cooled to -45°C under nitrogen. Methanesulfonyl chloride (3.5 mL, 45.5 mmol) was added followed by dropwise addition of TEA (9.75 mL, 70 mmol) over 5 minutes. The mixture was stirred at -45°C for 30 minutes. A solution of LiBr (12.2 g, 140 mmol) in THF (50 mL) was added dropwise over 15 minutes and the mixture was stirred at 0°C for 1 hour. The mixture was then poured into water (300 mL), and extracted with Et₂0 (x2). The combined organic layers were washed with saturated NaHC0₃ and brine, dried (Na₂S0₄), filtered and evaporated in vacuo to afford 8.65 g (90%) of the bromide.

Example 4

A solution of farnesol (5.0 g, 157.5 mmol) in THF (350 mL) was cooled to -45°C under nitrogen. Methanesulfonyl chloride (15.9 mL, 204.8 mmol) was added followed by dropwise addition of TEA (44.1 mL, 314.6 mmol) over 5 minutes. The mixture was stirred at -45°C for 45 minutes. A solution of LiBr (54.6 g, 630 mmol) in THF (350 mL) was added dropwise over 5 minutes and the mixture was stirred at 0°C for 1 hour. The mixture was then poured into water (300 mL), and extracted with Et₂0 (3x150 mL). The combined organic layers were washed with saturated NaHC0₃ (200 mL) and brine (200 mL), dried (Na₂S0₄), filtered and evaporated in vacuo to afford 38.8 g (86%) of the bromide.

Example 5

38.8 g (136 mmol) allylic bromide was dissolved in 200 ml of DMF and 75.9 g (462 mmol) benzene sulfuric acid sodium salt was added in one portion at room temperature. The suspension was stirred at room temperature for 18h over night. The mixture was poured into ice water. The layers were separated and the aqueous layer was extracted with EtOAc. The combined organic extracts were washed with ice water and ice cold brine, dried over Na₂S0₄, filtered and concentrated in vacuo by rotary evaporation at 40 °C. The residue was purified by dry flash. A gradient heptane:EtOAc (95:5) to heptane :EtO Ac (90: 10) was used as eluent to afford 35.42 g (75%) of pure sulfone.

Example 6

A solution of the bromide (8.65, 31.4 mmol) and the sulfon (7.28 g, 21.0 mmol) in THF (150 mL) was cooled to -45°C under nitrogen. A solution of t-BuOK (3.52 g, 31.4 mmol) in THF 60 mL) was added dropwise over 15 minutes. The resulting mixture was stirred at -45°C for 1 hour. The cooling bath was removed and saturated NH₄C1 (300 mL) was added carefully. The mixture was extracted with Et₂0 and the combined organic layers were washed with saturated NH₄C1, dried (Na₂S0₄), filtered and evaporated in vacuo. Flash chromatography (silica, heptane:EtOAc 9: 1) afforded 8.7 g (77%) of the product.

I PdCI₂(dppp)

A solution of the protected penteprenol (0.54 g, 1.0 mmol) in THF (15 mL) under N₂ at -78°C was added PdCl₂(dppp) (30 mg, 0.05 mmol). LiEt₃BH (1 M in THF, 4.0 mL, 4.0 mmol) was added dropwise over 15 minutes. The mixture was allowed to reach -30°C and was then stirred at this temperature overnight. The cooling bath was removed and 10%> NH₄C1 (50 mL) was added carefully. The mixture was extracted with Et₂0 (x2), and the combined organic phases were washed with 10% NH₄C1, dried (Na₂S0₄), filtered and evaporated in vacuo. Flash chromatography (silica, heptane:EtOAc 9: 1) afforded 300 mg (81%) of the product. Example 7

PBr₃,

THF, 4h, OX

10.83 g (30.20 mmol) allylic alcohol was dissolved in 60 ml of dry THF. At 0 °C, 1.5 ml (4.32 g, 15.96 mmol) PBr₃ were added drop wise via septum and syringe and the clear, colorless solution was stirred at 0°C for 4 h. The reaction was quenched by addition of ice cold water. The layers were separated and the aqueous layer was extracted with ether. The combined organic extracts were washed with NaHC0₃ and brine, dried over Na₂S0₄, filtered and concentrated in vacuo to give the bromide as colorless oil (10.89 g, 25.84 mmol, 86%>). The crude product was used for the next step without further purification.

1H NMR (200 MHz, CDC1₃) δ 5.56-5.47 (m, 1H), 5.18-5.01 (m, 4H), 4.00 (d, ³J=8.4 Hz, 2H), 2.18-1.84 (m, 16H), 1.71 (s, 3H), 1.67 (s, 3H), 1.58. CDC1₃ solvent peak: δ 7.24.

Example 8

PhS0₂Na,

DMF, 18h, 25°C

10.89 g (25.84 mmol) allylic bromide was dissolved in 200 ml of DMF and 21.30 g (129.75 mmol) benzene sulfuric acid sodium salt was added in one portion at room temperature. The suspension was stirred at room temperature for 18h over night. The mixture was poured into ice water. The layers were separated and the aqueous layer was extracted with EtOAc. The combined organic extracts were washed with ice water and ice cold brine, dried over Na₂S0₄, filtered and concentrated in vacuo by rotary evaporation at 40 °C. The residue was purified by dry flash. A gradient heptane: EtOAc (90: 10) to heptane:EtOAc (70:30) was used as eluent to afford 6.14 g (12.71 mmol, 50%) of pure sulfone as colorless oil and 2.92 g (6.05 mmol, 24%) of mixed fractions containing mostly sulfone as colorless oil.

Example 9

2-Bromo-l,4-dimethoxy-3 -methyl naphthalene was prepared by a modification of a method described in the literature (Adams, R., Geissman, B. R., Baker, B. R., Teeter, H. M. J ACS (1941) 61, 528.)

4.68 g (195 mmol) magnesium turnings were covered with dry THF and 0.5 ml (1.09 g, 5.80 mmol) 1,2-dibromo ethane was added via septum and syringe. The mixture stood for 30 min. 18.37 g (65.37 mmol) 2-bromo-l,4-dimethoxy-3 -methyl naphthalene dissolved in 30 ml of dry THF was added drop wise to the magnesium turnings over 30 min. The reaction mixture was cooled with a water bath, when it started to reflux. After that, the mixture was stirred at 35°C for 1 ,5h in a water bath until TLC showed complete conversion. The Grignard solution was used for the next step.

13.59 g (62.63 mmol) geranyl bromide dissolved in 100 ml of dry THF was added to 0.91 g (1.297 mmol) PdCl₂(PPh₃)2. To this yellow suspension, Grignard solution was added portion wise at room temperature. The mixture was stirred over night for 18h. The reaction was quenched at room temperature by addition of NH₄C1, the layers were separated and the aqueous layer was extracted with Et₂0. The combined organic extracts were dried over Na₂S0₄, filtered and concentrated in vacuo to give 23.44 g of a brown oil. The residue was dissolved in little CH₂C1₂ and was filtered through a plug of Si0₂ (50-60 g) to remove palladium residues. The plug was washed with CH₂C1₂ until all product was washed out (checked by TLC). The combined fractions were concentrated in vacuo. The crude product 2-(3,7-dimethyl- octa-2,6-dienyl)-l,4-dimethoxy-3-methyl-naphtalene was used in the next step without further purification.

1H NMR (200 MHz, CDC1₃) δ 8.07-8.03 (m, 2H), 7.47-7.42 (m, 2H), 5.13-5.07 (m, 2H), 3.88 (s, 3H), 3.86 (s, 3H), 3.56 (d, ³J=6.1 Hz, 2H), 2.37 (s, 3H), 2.03 (m, 4H), 1.82 (s, 3H), 1.63 (s, 3H), 1.56 (s, 3H); ¹³C NMR (50 MHz, CDC1₃) δ 150.07, 149.71, 135.63, 131.37, 130.91, 127.46, 127.24, 126.93, 125.36, 125.23, 124.20,

122.90, 122.25, 122.08, 62.15, 61.28, 39.63, 26.53, 26.31, 25.65, 17.64, 16.32, 12.32

Example 11

0.37 g (3.34 mmol) Se0₂, 0.94 g (6.81 mmol) salicylic acid and 23 ml of t-BuOOH (70 wt% in water) were suspended in 85 ml of CH₂C1₂. The suspension was stirred at room temperature for 40 min and then cooled to 0 °C with an ice bath. At 0 °C, 21.08 g (62.37 mmol) crude 2-(3,7-dimethyl-octa-2,6-dienyl)-l,4-dimethoxy-3- methyl-naphtalene dissolved in 45 ml of CH₂C1₂ was added in one portion. After stirring at 0 °C for 5h the suspension was diluted with 150 ml of toluene and the solvent was removed in vacuo by rotary evaporation at 40 °C. The residue was taken up in 150 ml of CH₂C1₂ and the red brown solution was washed with NaHC0₃, dried over Na₂S0₄, filtered and concentrated in vacuo by rotary evaporation at 30 °C. The residue was dissolved in 140 ml of dry THF and 7 ml of MeOH, cooled to 0 °C with an ice bath and 2.44 g (64.50 mmol) NaBH₄ was added portion wise. The mixture was stirred at 0 °C for 30 min and 50 ml of ice cold saturated NH₄C1 was added portion wise at 0 °C to quench the reaction. The layers were separated and the aqueous layer was extracted with Et₂0. The combined organic extracts were washed with brine, dried over Na₂S0₄, filtered and concentrated in vacuo by rotary evaporation at 30 °C to give a dark brown oil (21.48 g). The residue was purified by dry flash. A gradient heptane : EtOAc (80 : 20) to heptane : EtOAc (60 : 40) was used as eluent to afford 6.43 g (18.17 mmol, 28% over 3 steps from geraniol) of 8- (l,4-dimethoxy-3-methyl-naphtalen-2-yl)-2,6-dimethyl-octa-2,6-dien-l-ol as a oil. 1H NMR (200 MHz, CDC1₃) δ 8.06-8.01 (m, 2H), 7.48-7.40 (m, 2H), 5.34-5.28 (m, 1H), 5.12-5.05 (m, 1H), 3.92 (m, 2H), 3.86 (s, 3H), 3.54 (d, ³J=5.9 Hz, 2H), 2.36 (s, 3H), 2.14-2.03 (m, 4H), 1.70 (s, 3H), 1.61 (s, 3H).

Example 12

6.45 g (18.22 mmol) of 8-(l,4-dimethoxy-3-methyl-naphtalen-2-yl)-2,6-dimethyl- octa-2,6-dien-l-ol was dissolved in 45 ml of dry THF. At 0 °C, 0.9 ml (2.59 g, 9.58 mmol) PBr₃ was added drop wise via septum and syringe and the clear, colourless solution was stirred at 0°C for 3 h. The reaction was quenched by addition of ice cold water. The layers were separated and the aqueous layer was extracted with ether. The combined organic extracts were washed with NaHC0₃ and brine, dried over Na₂S0₄, filtered and concentrated in vacuo to give 2-(8-bromo-3,7- dimethyl-octa-2,6-dienyl)-l,4-dimethoxy-3-methyl-naphtalene as a colorless oil (6.29 g, 15.08 mmol, 83%). The crude product was used for the next step without further purification.

Example 13

9.06 g (18.76 mmol) (3,7,11,15, 19-pentamethyl-eicosa-2, 6, 10,14, 18-pentaene-l- sulfonyl)-benzene were dissolved in 80 ml of dry THF and the solution was cooled to -78 °C with C0₂ / MeOH. At -78 °C, 11.80 ml (18.88 mmol) BuLi (1.6 M solution in hexane) was added drop wise via septum and syringe over 10 min. The orange solution was stirred for 2.5 h at -78 °C. 6.07 g (14.56 mmol) 2-(8-bromo-3,7- dimethyl-octa-2,6-dienyl)-l,4-dimethoxy-3-methyl-naphtalene dissolved in 30 ml of dry THF was added via dropping funnel over 10 min. The brown reaction mixture was stirred at -78 °C for 1.5 h. At -78 °C, the reaction was quenched by addition of 50 ml of a Et₂0/MeOH mixture (1 : 1 v/v). The mixture was allowed to reach room temperature and after that 100 ml of saturated NH₄C1 solution was added. The layers were separated and the aqueous layer was extracted with Et₂0. The combined organic extracts were washed with brine, dried over Na₂S0₄, filtered and

concentrated in vacuo by rotary evaporation at 30 °C to give 16.21 g of 2-(9- benzenesulfonyl-3 ,7, 11 , 15 , 19,23 ,27-heptamethyl-octacosa-2,6, 10,14, 18,22,26- heptaenyl)-l,4-dimethoxy-3 -methyl -naphtalene as a brownish yellow oil, which was used in the next step without further purification. Example 14

16.21 g 2-(9-benzenesulfonyl-3,7,l 1,15,19,23, 27-heptamethyl-octacosa- 2,6,10,14,18,22,26-heptaenyl)-l,4-dimethoxy-3-methyl-naphtalene mixture was dissolved in 120 ml of dry THF and 0.57 g (0.96 mmol) PdCl₂(dppp) was added in one portion and the suspension was cooled to 0 °C with an ice bath. At 0 °C, 42.00 ml (42.00 mmol) LiEt₃BH (1.0 M solution in THF) were added portion wise via septum and syringe over 20 min. The dark brown solution was stirred at 0 °C for 7 h. At 0 °C, the reaction was quenched by addition 100 ml of saturated NH₄C1 solution. The layers were separated and the aqueous layer was extracted with Et₂0. The combined organic extracts were washed with saturated NH₄C1 solution, dried over Na₂S0₄, filtered and concentrated in vacuo by rotary evaporation at 30 °C to give 18.18 g of dark brown oil. It was purified by dry flash with CH₂C1₂ as eluent to afford 11.01 g of yellow oil, which was used in the next step without further purification. 1H NMR (200 MHz, CDC1₃) 6 8.09-8.01 (m, 2H), 7.49-7.41 (m, 2H), 5.11-5.08 (m, 7H), 3.88 (s, 3H), 3.86 (s, 3H), 3.57 (d, ³J=6.3 Hz, 2H) 2.38 (s, 3H), 2.05-1.85 (m, 24H), 1.83 (s, 3H), 1.68 (s, 3H), 1.60 (s, 12H), 1.57 (s, 6H); ¹³C NMR (50 MHz, CDCI₃) δ 150.07, 149.71, 135.71, 135.08, 134.92, 134.86, 127.46, 127.23, 126.89, 125.35, 125.23, 124.40, 124.25, 124.16, 124.01, 122.80, 122.25, 122.08, 62.14, 61.27, 39.71, 26.75, 26.65, 26.54, 26.31, 25.66, 17.66, 16.39, 15.99, 12.37

Example 15

2-(3 ,7, 11 , 15 , 19,23 ,27-heptamethyl-octacosa-2,6, 10,14, 18,22,26-heptaenyl)- 1 ,4- dimethoxy-3-methyl-naphtalene (8.50 g, 12.54 mmol) was suspended in 45 ml of acetonitrile, 45 ml of CH₂C1₂ and 20 ml of H₂0 and the suspension was cooled to 0 °C with an ice bath. At 0 °C, an ice cold solution of 17.26 g (31.48 mmol) CAN in 32 ml of acetonitrile and 32 ml of H₂0 was added portion wise via dropping funnel over 20 min. The orange mixture was stirred at 0 °C for 40 min. and at room temperature for 16.5 h over night. The yellow mixture was poured into 100 ml ice water. The layers were separated and the aqueous layer was extracted with CH₂CI₂. The combined organic extracts were washed with ice water, dried over Na₂S0₄, filtered and concentrated in vacuo by rotary evaporation at 40 °C to give 8.50 g of yellow oil. It was purified by dry flash. A gradient heptane : EtOAc (100 : 1) to heptane : EtOAc (95 : 5) was used as eluent to afford 4.93 g (7.61 mmol, 42% over 4 steps from 2-(8-bromo-3,7-dimethyl-octa-2,6-dienyl)-l,4-dimethoxy-3-methyl- naphtalene) of brownish yellow oil, which solidified in the fridge and was recrystallized from EtOAc and ethanol to give 3.5 g of MK7 as a bright yellow solid.

1H NMR (200 MHz, CDC1₃) δ 8.07-8.00 (m, 2H), 7.69-7.63 (m, 2H), 5.08-4.97 (m, 7H), 3.35 (d, ³J=6.9 Hz, 2H) 2.16 (s, 3H), 2.05-1.81 (m, 24H), 1.77 (s, 3H), 1.65 (s, 3H), 1.57 (s, 12H), 1.54 (s, 6H); ¹³C NMR (50 MHz, CDC1₃) δ 185.34, 184.40, 146.08, 143.27, 137.48, 135.15, 134.84, 133.25, 133.19, 132.13, 132.09, 131.15, 126.24, 126.13, 124.37, 124.23, 124.11, 123.80, 119.05, 39.68, 26.72, 26.65, 26.45, 25.96, 25.65, 17.63, 16.38, 15.97, 12.62

Claims

A process com rising reacting a compound of formula (X)

wherein Y is S0₂Ar or SAr;

Ar is a C6-10 aryl group or C7-12 arylalkyl group; and

p is 1 or 2;

with a compound of formula (XI)

wherein Ri is a hydroxyl protecting group, especially acetate;

LG is a leaving group such as halo; and

q is 1 to 2;

in the presence of a base so as to form a compound of formula XII

and (ii) converting said compound into a compound of formula XIII

2. A process as claimed in claim 1 for the preparation of a compound of formula (I)

where n is m + m' + 2;

comprising steps (i) and (ii) as defined in claim 1;

(iii) converting said compound of formula (XIII) to one of formula (V) or (VI)

wherein m is p+q (e.g. 3) and Ar is a C6-10 aryl group or C7-12 arylalkyl group; (iv) reacting said compound of formula (V) or (VI) with a compound of formula (Γ)

wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; m' is 0 to 8, e.g. 0 and X represents a leaving group;

in the presence of a base;

(v) reductively removing the arylthio or arylsulfonyl groups in the resulting compounds; and

(vi) converting by oxidation the diprotected naphthoquinone into a

naphthoquinone.

3. A process as claimed in claim 1 or 2 comprising reacting a compound of formul

wherein Y is S0₂Ar or SAr;

Ar is a C6-10 aryl group or C7-12 arylalkyl group; and

with a compound of formula (XI)

wherein Ri is a hydroxyl protecting group, especially acetate; and

LG is a leaving group such as halo;

in the presence of a base so as to form a compound of formula XII

(XII)

and (ii) converting said compound into a compound of formula XIII

e.g. by reduction such as using a lithium based reducing agent such as LiHBEt₃. (iii) converting said compound of formula (XIII) to one of formula (V) or (VI)

(VI)

wherein Ar is a C6-10 aryl group or C7-12 arylalkyl group;

(iv) reacting said compound of formula (V) or (VI) with a compound of formula (Γ)

wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; and X represents a leaving group;

in the presence of a base;

(vi) converting by oxidation the diprotected naphthoquinone into a

naphthoquinone; so as to form MK-7.

4. A process as claimed in claim 1 for the preparation of a compound of formula (I)

where n is m + m' +2;

comprising steps (i) and (ii) as defined in claim 1; iii) converting said compound of formula (XIII) to one of formula (VII) or (VIII)

(VII)

wherein m is p+q;

wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; m' is 0 to 8, and X represents a leaving group;

in the presence of a Ni, Cu or Pd catalyst; and

(v) converting the diprotected naphthoquinone into a naphthoquinone.

6. A process as claimed in claim 1 for the preparation of a compound of formula (I)

where n is m + m' + 2;

comprising steps (i) and (ii) as defined in claim 1; iii) converting said compound of formula (XIII) to one of formula

wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; m' is 0 8;

(v) reductively removing the arylthio or arylsulfonyl groups; and

7. A process as claimed in claim 1 for the preparation of a compound of formula (I)

where n is m + 2;

comprising steps (i) and (ii) as defined in claim 1; (iii) converting the compound of formula (XIII) into a compound of formula

(in);

wherein LG is a leaving group and m is the sum of p + q;

reacting said compound of formula (III) with a compound of formula

OR

'MgHal ~B(OH)₂

OR (II) OR (IV) wherein R is a hydroxyl protecting group such as an alkyl group or benzyl; in the presence of a copper, nickel or palladium catalyst; and

(v) converting the diprotected naphthoquinone into a naphthoquinone.

8. A process as claimed in claim 2 to 7 wherein oxidation of the diprotected naphthoquinone into a naphthoquinone is achieved using cerium ammonium nitrate (CAN).

9. A process as claimed in claim 2 to 8 wherein the compound of formula (I) is MK-7.

10. A process as claimed in claim 1 to 10 in which the arylthio or aryl sulphonyl reduction step is effected in the absence of a metal.

1 1. A process as claimed in claim 1 to 10 in which Ri is an ester protecting group.

or

wherein R is a hydroxyl protecting group other than methyl, e.g. a C₂-6 alkyl or benzyl and Y is S0₂Ar or SAr in which Ar is a C6-10 aryl group or C7-12 arylalkyl group.