Klyne and Stokes reported that the hydroxyl group at C-
22
in natural
22
-hydroxycholesterol (26) is α_F-oriented. In connection with studies on the synthesis of ecdysone in our laboratory, it was found that this assignment should be reversed. Lactone A (3) and B (4) were prepared from stigmasterol (1) by eight steps of reactions as key, intermediates for the synthesis of ecdysone and its isomer at C-
22
(41). These lactones were introduced into diol A (5) and B (6), respectively, which were also synthesized from stigmasterol by another route. 5α-Cholestane-3β,
22
-diol (15a), in which the configuration at C-
22
is apparently different from that of natural
22
-hydroxycholesterol, was obtained by transformations from diol A (5). (Chart 2) The similar treatment of diol B (6) afforded 5α-cholestane-3β,
22
-diol (25b) identical with the hydrogenation product of natural
22
-hydroxycholesterol. (Chart 3) On the other hand,
22
-isoecdysone (41) was synthesized from lactone A (3) (Chart 4), and ecdysone from lactone B (4). Thus, the configuration of the
22
-hydroxyl group in natural
22
-hydroxycholesterol is the same as that of ecdysone. If the configuration assigned in ecdysone is considered to be unequivocal, natural
22
-hydroxycholesterol must be formulated as 5-cholestene-3β,
22
β_F-diol.
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