Sugars, synthesis, 2- thiazole

A. Dondoni, G. Fantin, M. Fogagnolo, and P. Pedrini, Stereochemistry associated with the addition of 2-(trimethylsilyl)thiazole to differentially protected a-amino aldehydes. Applications toward the synthesis of amino sugars and sphinogosines, J. Org. Chem. 55 1439 (1990). 

Thiazole-based one carbon extension has been proved to be a useful tool in the synthesis of C-branched sugar derivatives [37]. To investigate an approach towards the synthesis of... 

C-branched sugar aceric acid [32] (O Scheme 21), 3-ulose 68 was treated with 2-(trimethylsi-lyl) thiazole (2-TST) in THF under thermodynamic control, followed by desilylation with tetra- -butylammonium fluoride (TBAF), led to a 5 1 mixture of endo- and exo-adducts 69 and 71, respectively. In contrast, addition of 2-thiazolyl lithium to compound 68 gave only the adduct 71, arising from sterically controlled exo-addition to the trioxabicylo[3.3.0]octane ring system in an unoptimized 40% yield. Benzylation of isomeric adducts 69 and 71 afforded 3-0-benzyl derivatives 70 and 72, respectively. The stereochemistry of thiazole addition to 3-ulose 68 was established by X-ray structural analyses of compounds 69 and 72, which revealed that 72 has the required C-3 conflguration for aceric acid synthesis. 

A comprehensive review (260 refs.) on the synthesis of carbohydrates from noncarbohydrate sources covers the use of benzene-derived diols and products of Sharpless asymmetric oxidation as starting materials, Dodoni s thiazole and Vogel s naked sugar approaches, as well as the application of enzyme-catalysed aldol condensations. The preparation of monosaccharides by enzyme-catalysed aldol condensations is also discussed in a review on recent advances in the chemoenzymic synthesis of carbohydrates and carbohydrate mimetics, in parts of reviews on the formation of carbon-carbon bonds by enzymic asymmetric synthesis and on carbohydrate-mediated biochemical recognition processes as potential targets for drug development, as well as in connection with the introduction of three Aldol Reaction Kits that provide dihydroxyacetone phosphate-dependent aldolases (27 refs.). A further review deals with the synthesis of carbohydrates by application of the nitrile oxide 1,3-dipolar cycloaddition (13 refs.). ... 

In connection with studies on the synthesis of complex cell wall glycans, we have developed effective syntheses of the novel branched sugar aceric acid and its C-2 epimer. Control of asymmetry in the installation of the key tertiary centers was effected by either asymmetric dihydroxylation of an appropriate alkene derivative or by thiazole addition to the corresponding ketone. 

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