Tanaka Hideya, Noguchi Hiroshi, Abe Ikuro
University of Shizuoka, School of Pharmaceutical Sciences, 2-1 Yada, Shizuoka 422-8526, Japan.
Org Lett. 2004 Mar 4;6(5):803-6. doi: 10.1021/ol036509r.
1-methylidenesqualene and 25-methylidenesqualene were converted to 30-methylidenehop-22(29)-ene by squalene:hopene cyclase from Alicyclobacillus acidocaldarius. It was remarkable that both analogues generated the same product. The hopanyl intermediate cation, stabilized by the methylidene residue, enabled a rotation of the isobutenyl group at C-21 prior to the final proton elimination. In contrast, in the formation of hop-22(29)-ene, the final proton abstraction takes place regiospecifically from the Z-methyl group, which was verified by cyclization of (1,1,1,24,24,24-(2)H(6))squalene into (23,23,23,30,30,30-(2)H(6))hop-22(29)-ene. [reaction: see text]
1-亚甲基角鲨烯和25-亚甲基角鲨烯被嗜酸 Alicyclobacillus acidocaldarius 的角鲨烯：藿烯环化酶转化为30-亚甲基何帕-22(29)-烯。值得注意的是，这两种类似物生成了相同的产物。由亚甲基残基稳定的藿烷基中间体阳离子，使得在最终质子消除之前，C-21处的异丁烯基能够发生旋转。相比之下，在何帕-22(29)-烯的形成过程中，最终的质子夺取是从Z-甲基区域特异性地发生的，这通过(1,1,1,24,24,24-(2)H(6))角鲨烯环化为(23,23,23,30,30,30-(2)H(6))何帕-22(29)-烯得到了验证。[反应：见正文]
