Biocatalytic oxidative kinetic resolution of sec-alcohols: stereocontrol through substrate-modification
摘要:
Whole lyophilised cells of Rhodococcus ruber DSM 44541 were employed for the oxidative kinetic resolution of sec-alcohols using acetone as hydrogen acceptor. The enantioselectivity of this process could be controlled effectively by introducing C-C multiple bonds into substrates, which were inefficiently recognised, in particular short-chain (omega-1)-alcohols and (omega-2)-analogs. Thus, the enantioselectivities of rac-2-pentanol (E= 16.8) and rac-3-octanol (E= 13.3) were significantly improved by introducing a C=C bond adjacent to the alcohol moiety to give racemic (E)-pent-3-en-2-ol and 4-(E)-octen-3-ol, which were resolved with excellent selectivities (E >100 and 50, respectively). In addition, it was found that high stereodifferentiation between the E- and Z-configured double bonds occurred, as the corresponding (Z)-isomers were not converted. Similar selectivity-enhancing effects were observed with acetylenic analogs. (C) 2003 Elsevier Science Ltd. All rights reserved.
5—Endo ring closures of allylic hydroperoxides: Useful routes to 1,2—dioxolanes involving strongly stereoselective free radical and polar reactions
作者:John L. Courtneidge、Melanie Bush、Lay See Loh
DOI:10.1016/s0040-4020(01)92274-4
日期:1992.1
Intramolecular cyclisation of simple allylic hydroperoxides to give substituted 1,2—dioxolanes using electrophilic reagents has been investigated. Closure using mercury(II) acetate and electrophilic halogen reagents (NBS, Br2 ButOC1) occurs by Markovnikov—directed and conformationally strict stereospecificity. Subsequent free— radical reaction of the mercurated dioxolanes involved specific reaction
已经研究了使用亲电子试剂将简单的烯丙基氢过氧化物分子内环化以生成取代的1,2-二氧戊环的方法。使用乙酸汞(II)和亲电卤素试剂(NBS,Br 2 Bu t OC1)封闭是由马尔科夫尼科夫(Markovnikov)指导的,构象严格的立体特异性。随后,汞化二氧戊环的自由基反应涉及特定的反应,该反应涉及来自中间体二氧戊环基自由基的空间未保护面的反应。
A Simple Entry to the 5,8-Disubstituted Indolizidine Skeleton via Hetero Diels-Alder Reaction
作者:Juan Francisco Rodríguez-Caro、María M. Afonso、José Antonio Palenzuela
DOI:10.3390/molecules28217316
日期:——
short, simple, and general synthesis of these alkaloids based on the heteroDiels–Alderreaction between suitable monoactivated dienes and Δ1-pyrroline as the dienophile. The selectivity of the process is explained based on computational studies. Concise synthesis of the indolizidine alkaloid 181B from a heteroDiels–Alderreaction was accomplished in four steps.