1-Thiosugars

The 17-hydroxy group of 2,3-epithiosteroids and the hydroxy groups of some epi-thiosugars may be acylated with acid anhydrides or chlorides without affecting the episulfide (77CPB1140). 

Stereocontrolled synthesis of thiosugars from acyclic precursors and preparation of pseudonucleosides with thiosugar moiety 97YGK186. 

Butler et al. [32] also developed a series of O-acylated-S-nitrosated thiosugars (Fig. 8.5). Partial de-acylation in tissue should give a mixture of hydrophilic and hydrophobic groups. These compounds can be delivered transdermally and result in greatly enhanced subcutaneous blood flow [33]. Unfortunately, these compounds are not very stable and cannot be isolated. The alcoholic solution, in which they are stored and administered, must be kept on ice during use. 

Carbohydrate derivatives, in which one or more of the oxygen atoms bonded directly to the carbon skeleton have been replaced by sulfur, are termed thiosugars. The placement of the sulfur atom at the anomeric position constitutes a special case, because thioglycosides, alkyl, aryl and heterocyclic, occupy a very important place as versatile glycosyl donors in glycosidation methodology. Anomeric thiocarbonyl compounds, on the contrary, have been less explored, although their potential and scope is likely to be similar. 

The same thiosugar derivatives were condensed with the monobrominated porphyrin 123 in dry DMF, giving rise to the expected compounds 124b in good yields and from these, by cleavage of the acetyl groups, the desired compounds 124a have been obtained (Scheme 18).81... 

Instead of a triflate, the electrophile on the glycosyl acceptor can be an a,(3-unsaturated carbonyl group. This is the case reported in Fig. 25, in which a stereoselective Michael addition of the 1-thiosugar 56 to the a,(3-conjugated system of levoglucosenone 57, generated after deprotection a couple of L-fucopyranosyl-4-thiodisaccharides 61 and 62 presenting inhibitory activity on a-L-fucosidase.54... 

S -Alkyl thiocarbamates (Table 4.24) have been synthesized [I] by a procedure (Scheme 4.19) which is closely analogous to that employed for the preparation of S-alkyl thiocarbonates (see Section 4.1), S-Glycosyl dithiocarbamates [2], which are useful precursors for thiosugars, have been prepared by simple nucleophilic displacement of the tosyloxy group by the N,N-diethyldithiocarbamate anion (cf preparation of S-glycosyl dithiocarbonates, 4.1.13). 

Witczak, Z. J. Chhabra, R. Chen, H. Xie, X. Q., Thiosugars.2. A novel approach to thiodisaccharides - The synthesis of 3-deoxy-4-thiocellobiose from levoglucosenone. 

M. Fuzier, Y. Le Merrer, and J.-C. Depezay, Thiosugars from D-mannitol, Tetrahedron Lett., 36 (1995)6443-6446. 

Thiosugars constitute another class of carbohydrate analogs presenting interesting biological and pharmacological properties [105, 106]. 

Scheme 48 Synthesis of butenolides fused to pento- or hexopyranoses and thiosugar analogs from furanos-3-nloses...

Being restricted to DHAP as the nucleophile, aldol additions will only generate ketoses and derivatives from which aldose isomers may be obtained by biocatalytic ketol isomerization (cf. Sect. 7.1) [306]. For a more direct entry to aldoses the inversion strategy may be followed (Scheme 19) [290] which utilizes monoprotected dialdehydes. After aldolization and stereoselective chemical or enzymatic ketone reduction, the remaining masked aldehyde function is deprotected to provide the free aldose. Further examples of the directed, stereodivergent synthesis of sugars and related compounds such as aza- or thiosugars are collected in Sect. 7. 

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