not avoided by utilizing only E-allylic alcohols. In this way one obtains the erythro diol relationship by DIBAL reduction of, for example, 18 to the corresponding erythro aldehyde. Whereas, treatment of 18 with K2C03 in MeOH leads, via epimerization, to an almost quantitative yield of the corresponding threo aldehyde. The epimerization process is general, and we have used it in highly selective syntheses of all four pentoses and all eight hexoses.
Aus dem geschützten Epoxy‐alkohol (I) entstehen isomere Bis‐epoxide (II), die zu stereoisomeren Tetrolen und ihren Derivaten (III) hydrolysiert werden können.
Die jeweils aus dem Aldehyd (I) nach bekannten Verfahren zugänglichen epimeren Epoxide (II) werden über die Stufen (III) in die Acetoxy‐thioacetale (IVa) bzw. (IVb) übergeführt, aus denen 1. mit Diisobutyl‐AIH die Isopropyliden‐Zucker(V) bzw. (VII) , 2. durch Behandlung mit K2CO3 /Methanol dagegen deren Epirneren (VI) bzw. (VIII) gebildet werden.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.