Glycal

About: Glycal is a research topic. Over the lifetime, 897 publications have been published within this topic receiving 17422 citations.

Highly Stereoselective β-Anomeric Glycosidation of a 2‘-Deoxy Syn-5‘-Configured 4‘-Spironucleoside

Abstract: A direct enantioselective pathway that delivers exclusively the β-anomer of a 4‘-spironucleoside has been successfully developed. The key starting material is the enantiomerically pure dihydroxy lactone 19, which has proven amenable to conversion to glycal 22 via the chloro acetonide. This intermediate is then capped as the 3,5-O-(tetraisopropyldisiloxane-1,3-diyl) glycal. The latter can enter into N-iodosuccinimide-promoted glycosidation with persilylated thymine. Only the β anomer is formed. Ensuing deiodination and desilylation proceed quantitatively to furnish the targeted, previously elusive anomer.

Studies on ketoses, 11. Pyranoid exo‐ and endo‐glycals from D‐fructose and L‐sorbose: Practical routes for their acquisition and some ensuing reactions

Abstract: The reductive elimination of the benzoylated β-D-fructopyranosyl and α-L-sorbopyranosyl bromides 10 and 23 has been examined in order to determine suitable conditions for effecting the elimination from the exo- as well as the endo-positions. Exposure of 10 and 23 to Zn/HOAc or Zn/N-methylimidazole gave the tribenzoates of exo-D-fructal (1) and exo-L-sorbal (25), in yields of 79 and 80%, respectively; minor products (ca, 10% each) were the corresponding endo-D-fructal (6) and endo-L-sorbal esters (26). For the reductive elimination to occur primarily from the endo-position, enhancement of the leaving group capacity of the respective ring acyloxy group was required, and materialized via the 3-O-mesyl analogues of fructosyl bromide 10, which smoothly reacted with Zn/HOAc to give the endo-D-fructal esters 20 and 21; their yields, over the five steps from diacetone-fructose, were in the 50% range. Accordingly, the methodology for generating ketose-derived glycal esters in exo- or endo-version, is now available. Some ensuing reactions of the exo-glycals have been exploited, that is, their ozonolysis to the respective pyranoid pentonolactones, and their hydrogenation to 1,5-anhydro-6-deoxy-hexitols.