catalyst furnished the β-hydroxy thioamide in good yield and enantioselectivity. On further transformation, the thioamide functionality was converted to the corresponding β-hydroxy ester. Finally, a convergent synthesis of the western zone of caprazamycin B was achieved by connecting the hemiester, the β-hydroxy ester, and the 2,3,4-tri-O-methyl-l-rhamnose fragments.
A Chiral Bifunctional Sulfonamide as an Organocatalyst: Alcoholysis of σ-Symmetric Cyclic Dicarboxylic Anhydrides
作者:Shigeki Sano、Takashi Honjo、Takeshi Tsumura、Yoshimitsu Nagao、Kentaro Yamaguchi、Yoshihisa Sei
DOI:10.1055/s-0029-1218374
日期:2009.12
Enantioselective alcoholysis of σ-symmetric cyclicdicarboxylicanhydrides with benzyl alcohol catalyzed by a chiralbifunctionalsulfonamide was achieved in up to 98% ee at 5 mol% loading.
AbstractCaprazamycin A has significant antibacterial activity against Mycobacterium tuberculosis (TB). The first total synthesis is herein reported and features a) the scalable preparation of the syn‐β‐hydroxy amino acid with a thiourea‐catalyzed diastereoselective aldol reaction, b) construction of a diazepanone with an unstable fatty‐acid side chain, and c) global deprotection with hydrogenation. This report provides a route for the synthesis of related liponucleoside antibiotics with fatty‐acid side chains.
Total Synthesis of Caprazamycin A: Practical and Scalable Synthesis of <i>syn</i>-β-Hydroxyamino Acids and Introduction of a Fatty Acid Side Chain to 1,4-Diazepanone
Diastereoselective aldol reactions of aldehydes 12 and 25-27, derived from uridine, with diethyl isocyanomalonate 13 and phenylcarbamate 21 were investigated using thiourea catalysts 14 or bases to synthesize syn-β-hydroxyamino acidderivatives. The 1,4-diazepanone core of 1 was constructed using a Mitsunobu reaction, and the fattyacid side chain was introduced using a stepwise sequence based on model studies.