Diastereoselective synthesis of 10b-substituted hexahydropyrroloisoquinolines from l-tartaric acid. Creation of a quaternary carbon stereocentre via N-acyliminium ion cyclization
摘要:
A simple, three-step synthesis of 10b-substituted-hexahydropyrroloisoquinolines 12-17 starting from an L-tartaric acid derived imide is described. The methodology presented employs the addition of a Grignard reagent to the imide carbonyl group, followed by a one-pot acetylation-cyclization sequence. The crucial step, an acid-catalyzed carbon-carbon bond forming reaction via an N-acyliminium ion offers moderate to high stereoselectivity, which has been shown to be strongly dependent on the size of the R-substituent. The mixtures of pyrroloisoquinolines obtained can be separated as enantiomerically pure 2-silyloxy-derivatives. (C) 2004 Elsevier Ltd. All rights reserved.
The synthesis of novel, enantiomericallypure C2-symmetrical hemiaminal ethers and diamines containing piperazine core is presented. The key steps of the synthesis involve the dimerization of an in situ generated α-amino aldehyde into the corresponding cyclic bis-hemiaminal, followed by dehydration in the presence of a base to give a 7-oxa-2,5-diaza-bicyclo[2.2.1]heptane derivative, which can be regarded
Heck Cyclization Strategy for Preparation of Erythrinan Alkaloids: Asymmetric Synthesis of Unnatural (−)-Erysotramidine from <scp>L</scp>-Tartaric Acid
was synthesized for the first time. The synthesis features the use of the enantiopure synthon, prepared in a set of highlystereoselective reactions, including N-acyliminium cyclization, dihydrofuranyl ring formation via silver-catalyzed intramolecular alcohol addition to acetylene, and vinylether catalytic hydrogen reduction. The crucial step of the synthesis, assembly of ring A, was achieved by using