Department of Chemistry, IISER Bhopal, Bhopal Bypass Road, Bhauri, Bhopal - 462 066, Madhya Pradesh, India.
Org Biomol Chem. 2019 Aug 14;17(30):7140-7143. doi: 10.1039/c9ob01373c. Epub 2019 Jul 17.
This report features the first catalytic asymmetric total synthesis of a sesquiterpene, (+)-ar-macrocarpene (1), in 7 steps with 42.1% overall yields from commercially available inexpensive 5,5-dimethylcyclohexane 1,3-dione. This strategy relies on a key [3,3]-sigmatropic rearrangement effecting reductive transposition through allylic diazene rearrangement (ADR) in a single step from intermediate allylic alcohol (+)-12 under the Mitsunobu reaction conditions with o-nitrobenzenesulfonyl hydrazide (o-NBSH). Enantioselective reduction of α-bromo vinylogous ester 16 under the Corey-Bakshi-Shibata reduction conditions forges the required stereocenter in the allylic alcohol (+)-12 in a highly enantioenriched manner (95% ee).
本报告以商业可得的廉价 5,5-二甲基环己烷-1,3-二酮为起始原料，经 7 步反应，以 42.1%的总收率，首次实现了倍半萜（+）-ar-大根香叶烯（1）的催化不对称全合成。该策略依赖于关键的[3,3]-σ重排效应，通过烯丙基重氮烯（ADR）在Mitsunobu 反应条件下，从中间体烯丙醇（+）-12 一步实现还原重排，得到邻硝基苯磺酰肼（o-NBSH）。在 Corey-Bakshi-Shibata 还原条件下，对α-溴代乙烯基酯 16 进行对映选择性还原，以高对映体过量（95%ee）的方式在烯丙醇（+）-12 中构建所需的立体中心。
