Total synthesis of reblastatin: convenient preparation of coupling partners and scaled assembly
作者:Chuancai Bian、Rui Yan、Xiaoming Yu
DOI:10.1016/j.tet.2014.03.020
日期:2014.5
Potentially scalable total synthesis of reblastatin was achieved based on Panek's previous study. Novel and convenient synthetic routes were developed for the known C8-C20 and C1-C7 coupling partners. The challenging C8-C20 fragment was prepared from TBS protected (S)-5-(hydroxymethyl)dihydrofuran-2(3H)-one (6) in nine steps (20% overall yield), and the C1-C7 fragment was synthesized from commercially available 3,4,6-tri-O-acetyl-D-glucal (9) in eight steps (35% overall yield). On a larger scale, Panek's eight-step assembly of the target molecule from the two partners was also slightly modified, giving 45 mg reblastatin (19% overall yield) in the first batch synthesis. Notable feature of our study is the settlement of the C14 chirality through a diastereoselective alpha-alkylation of 6 followed by a three-step full reduction of the lactone carboxyl, making vastly available 6 a universally applicable C11-C14 synthon for benzenoid/benzoquinone ansamycins. (C) 2014 Elsevier Ltd. All rights reserved.