(3S,15R)-15-(Benzyloxy)-3-[(tert-butyldimethylsilyl)oxy]-17-iodoandrosta-5,16-diene (3) was prepared from the corresponding 17-hydrazone9with iodine in the presence of tetramethylguanidine. The vinyl iodide3was converted into the corresponding organocuprate and conjugate additions of the latter were performed with both (E)- and (Z)-6-methylhept-2-en-4-one (4aand4b, respectively). In each case, the resulting adduct5awas obtained exclusively with the unnatural 20Sconfiguration. (3S,15R)-15-(Benzyloxy)-3-[(tert-butyldimethylsilyl)oxy]androsta-5,16-diene (13) and the corresponding 17,17' homocoupling product14were obtained as byproducts. When the addition to theE-enone was repeated in the presence of chloro(trimethyl)silane, the yield of the conjugate addition product improved, but the stereochemistry at C-20 remained the same.
(3
S,15
R)-15-(苄氧基)-3-[(
叔丁基二甲基硅基)氧基]-17-
碘雄甾-5,16-二烯(
3)是通过将相应的17-酰
肼9与
碘在四甲基
脲存在下反应制备而成。然后将烯丙基
碘3转化为相应的
有机铜试剂,并与(
E)-和(
Z)-6-甲基庚-2-烯-4-酮(
4a和
4b)进行共轭加成。在每种情况下,所得到的加合物
5a都是具有非天然的20
S构型。同时,作为副产物,还得到了(3
S,15
R)-15-(苄氧基)-3-[(
叔丁基二甲基硅基)氧基]雄甾-5,16-二烯(
13)和相应的17,17'同偶联产物
14。当在
氯化三甲基
硅存在下重复对
E-烯酮进行加成时,共轭加成产物的收率有所提高,但C-20的立体
化学结构仍然相同。