Thermal and Catalytic Diels-Alder Reactions Between (2E)-4, 5,6-Tri-O-acetyl-2,3-dideoxy-aldehydo-D-erythro -Hex-2-Enose and Cyclopentadiene

Abstract

Thermal and catalytic reactions between (2E)-4,5,6-tri-O-acetyl-2,3-dideoxy- aldehydo- d-erythro-hex-2-enose (1) and cyclopentadiene led, in each case, to the four stereoisomeric 5-formyl-6-(1,2,3-tri-O- acetyl-d-erythro-triol-1-yl)bicyclo[2.2.1]hept-2-enes (2-5). The role of the catalysts is discussed, and the face selectivity is rationalized in terms of both steric and electrostatic arguments. Upon subsequent sodium borohydride reduction, iodination, and zinc reduction, the adducts 2-5 were converted to their respective primary alcohols 6-9, that could be separated by column chromatography. Sequential basic deacetylation, oxidative cleavage of the sugar side-chain with sodium metaperiodate, and reduction with sodium borohydride, yielded the previously known (5R,6R)- or (5S, 6S)-bis(hydroxymethyl)norbornene-diols 12 or 13, thus establishing the C-5 and C-6 absolute configurations of their synthetic precursors.