Synthesis of All Stereoisomeric Carbapentofuranoses
摘要:
All carbocyclic analogs of the pentofuranoses were synthesized starting from norborn-5-en-2-one (1). By using either base- or acid-catalyzed Baeyer-Villiger reaction of 1, the central intermediates 2 and 3 were obtained. The required functionalization of the olefinic double bond was achieved either by cis-hydroxylation in the case of the ribo, lyre, and alpha-xylo derivatives or by epoxidation and subsequent opening with aqueous perchloric acid. In the latter case, a pronounced selectivity for opening the epoxy alcohol in the 3-position was found. If an epoxy acetate with both functions on the same side of the ring was used, the epoxide was opened in the 2-position by neighboring group participation of the acetate. The requisite side chain degradation was accomplished either by conversion of the ester into an olefin and subsequent dihydroxylation/cleavage reaction or by Curtius rearrangement to the amine and its conversion into an acetate.
Transformation of D-erythrose to some pseudoaldopentofuranoses. Syntheses of (1S,2R,3S,4S)-, (1R,2R,3S,4S)-, and (1R,2S,3S,4S)-2,3,4-trihydroxy-1-(hydroxymethyl)cyclopentanes and (1R,2S,3R,4R)-2,3-dihydroxy-4-(hydroxymethyl)-1-cyclopentanamine