A SCALEMIC SYNTHESIS OF THE SCOPADULCIC ACID SKELETON .2. RING-D FORMATION VIA REGIOSPECIFIC INTRAMOLECULAR ALDOL AND ALKYLATION REACTIONS

摘要

The propensity of abietenones such as 2 to form exclusively the extended enol(ate) into ring-B can be curbed by introducing an alkoxy group at C-7 in the abietane framework. Thus, the 7-trimethylsilyloxy enone-aldehydes 11 and 13 cyclize to form only the C-12 aldol products 12 and 14. Furthermore, the 9-iodoethyl-12-methyl-enone 19 cyclizes via its putative enol to give only the tetracyclic enone 20. Compounds 12 and 20 contain the complete carbon skeleton of scopadulcic acid B. Copyright (C) 1996 Elsevier Science Ltd [References: 4]