Titanium tetrachloride-mediated aza Diels–Aldercycloaddition using a chiral diene and an aza dienophile proceeds in highly diastereoselective manner to form a dehydropiperazic acid derivative in high yield, and diastereoselectivity of the reaction depends on the quantity of titanium tetrachloride.
The highly efficient synthesis of (R)- and (S)-piperazic acids, components of naturally occurring antibiotic cyclodepsipeptides, was achieved in 80% overall yield by the use of a proline-catalyzed asymmetric alpha-hydrazination as the key step. (C) 2004 Elsevier Ltd. All rights reserved.
A Scalable Process to the Key Intermediate of Cilazapril, (<i>S</i>)-1-Benzyloxycarbonylhexahydropyridazine-3-carboxylic Acid, Through a Novel Cascade Course
作者:Yu Chen、Yuwei Lu、Qing Zou、Huansheng Chen、Dawei Ma
DOI:10.1021/op400155u
日期:2013.9.20
A novel and efficient manufacturing technology is disclosed in the present work for the preparation of (S)-1-benzyloxycarbonylhexahydropyridazine-3-carboxylic acid, which is a keyintermediate of cilazapril. The whole process includes only three steps; the first two steps were conducted in one pot, followed by a novel selective removal of a Cbz group in a cascade course.