Enantio-controlled synthesis of the crocyclic C14-C23 subunit of cytochalasin b |
| |
Authors: | L. Thijs E.H.M. Stokkingreef J.M. Lemmens B. Zwanenburg |
| |
Affiliation: | Department of Organic Chemistry, University of Nijmegen, Toernooiveld 6525 ED NijmegenThe Netherlands |
| |
Abstract: | The synthesis of the C14-C23 macrocyclic subunit of cytochalasin B from pulegone is described. The key feature of this synthesis is the photo-induced rearrangement of epoxy diazomethyl ketone E to a γ-hydroxy alkenoic ester (Scheme 2). The intermediate epoxy alcohol F was prepared using the asymmetric Sharpless epoxidation. Considerable attention was given to the preparation of allylic alcohol 14, having a t-butyldimethylsilyloxy protecting function, as starting material for the asymmetric epoxidation, however, several unforeseen difficulties were encountered (Schemes 3 and 4). Satisfactory results were obtained using the methoxy group as protecting function (Scheme 5). The allylic alcohol 22 was prepared from bromide 20 by chain lengthening with propargyl alcohol. The Sharpless epoxidation of 22 took place with high induction. Conversion to epoxy ester 24, to diazo ketone 25 and photo-rearrangement to 26 and deprotection to give 28, completes the sequence. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|