Abstract
Total syntheses of the unique pyrrole derivatives (2a–d) and the steroid analogue (1) are reported. Reductions of the above imines with sodium borohydride or by a catalytic procedure have been found to be stereospecific, yielding only the trans-amine in each case. Metal–ammonia reductions of the benzoxe-pino-(2a) and benzocyclohepteno-pyrrole (2d) provided a 2:1 mixture of the corresponding trans- and the cis-amine respectively. Reductions of the indole derivative (2e) with lithium aluminium hydride, sodium in liquid ammonia, or by a catalytic method furnished in each case the cis-amine (22b). The rate of reduction of (2e) with sodium borohydride was much slower, and under special conditions it afforded a 3:1 mixture of the cis-(22b) and the trans-amtne (22a) respectively. The reasons for the completely different stereochemical results observed in the reductions of the imines (2a–d) and (2e) have been briefly discussed.
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More From: Journal of the Chemical Society, Perkin Transactions 1
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