Synthetic routes to methyl 3-deoxy-aldulosonic acid methyl esters and their 2-deoxy isomers based on the Horner-Emmons and Peterson reaction of sugar lactones

Abstract

The two reagents: 2-trimethylsilyl- and 2-[bis(2,2,2-trifluoroethoxy)phosphoryl]-1,3-dithianes were engaged in the construction of appropriate ketene thioacetals from the isomeric 2-deoxy-hexono-1,5-lactones via Horner-Emmons or Peterson reaction. A comparison of the results shows that the second reagent is more promising, as it forms the desired ketene thioacetals as sole products. The latter were directly transformed stereoselectively into the title α ulosonates in an oxidative hydrolysis reaction, using NBS/MeOH in CH 2Cl 2. A construction of the methyl 2-deoxy-ulosonates involved a preceding hydrogenation of the double bond by LiBH 4-TMSCl species, and subsequent hydrolysis with NBS in aqueous THF medium.