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Paper | Regular issue | Vol 36, No. 7, 1993, pp.1601-1616
Published online, 1st January, 1970
DOI: 10.3987/COM-93-6367
■ Synthesis of Thioaldehydes Having Optically Active Alkoxy Moiety and Their Asymmetric Hetero Diels-Alder Reaction

Tamiko Takahashi, Noriyuki Kurose, Toru Koizumi,* and Motoo Shiro*

*Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama, Toyama 930-0194, Japan

Abstract

Optically active α-alkoxycarbonylthioaldehydes (2a-g) were prepared using 8-arylmethols as chiral auxiliaries. Their asymmetric hetero Diels-Alder reactions with cyclopentadiene gave the endo cycloadducts (3 and 4) and exo cycloadducts (5 and 6) with moderate diastereomeric excesses. However, the major endo cycloadducts (3b-g) were isolated in optically pure form. This is the first chiral synthesis of 2-thiabicyclo[2.2.1]hept-5-ene ring system. The absolute configuration of the cyclic carbonate (12), which was prepared from the major endo cycloadduct (3c) via the epimerization, or the minor exo compound (6c), was determined as 1R by X-ray analysis. The cycloadduct (3c) was transformed to a potential intermediate (14) for the synthesis of carbocyclic homonucleosides.