New facile alkoxycarbonylating agent, alkyl pyrazole-1-carboxylates. The preparation and the utilities
摘要:
Alkyl pyrazole-1-carboxylates (2), which were readily prepared from alkyl chloroformate or carbazate in good yields, were provided as the new facile alkoxycarbonylating agents toward the Grignard reagents for the synthesis of one carbon higher carboxylic esters. Also amines were alkoxycarbonylated by 2 to produce the corresponding urethanes even in an aqueous medium. Benzyl 3,5-dimethylpyrazole-1-carboxylate (2d) could be utilized for the Cbz-protection of amino acids and esters in good yield without any racemization. (C) 1998 Elsevier Science Ltd. All rights reserved.
Enantioselective reduction of CO and CN compounds with NADH model N,N,1,2,4-pentamethyl-1,4-dihydronicotinamide
作者:Jos P. Versleijen、Mireille S. Sanders-Hovens、Sylvia A. Vanhommerig、Jozef A. Vekemans、Emmo M. Meijer
DOI:10.1016/s0040-4020(01)87253-7
日期:1993.8
The scope and mechanism of enantioselective hydride transfer from NADHmodel 4 to prochiral CO and CN compounds were investigated. Efficient chirality transfer from 4 to α-keto esters and α-methoxycarbonylimino esters was achieved. The resemblance in reactivity and stereochemistry of the prochiral CO and CN-CO2Me functionalities in the hydride transfer reaction is attributed to the intervention
Intramolecular amidoalkylation of aromatics II. Synthesis of conformationally restricted bridged peptides analogues of phg-gly or gly-phg.
作者:Dov Ben-Ishai、Aharon R. McMurray
DOI:10.1016/s0040-4020(01)80154-x
日期:1993.1
Derivatives of Phg-α-MeO-GlyOH() and its isomer α-MeO-Gly-Phg() were prepared and their inter and intramolecular amidoalkylation reactions were studied. Derivatives of underwent smooth cyclization to give 4-amino-3-isoquinolon-1-carboxylic acid derivatives (, ). The isomer , which reacted smoothly intermolecularly with toluene to give the open chain peptide , reacted sluggishly intramolecularly.