Diastereoselective preparation of novel tetrahydrooxazinones via heterocycloaddition of N-Boc, O-Me-acetals
作者:Patricia Gizecki、Ramzi Ait Youcef、Céline Poulard、Robert Dhal、Gilles Dujardin
DOI:10.1016/j.tetlet.2004.10.154
日期:2004.12
Under Lewis acid conditions, reaction of N-Boc, O-Me acetals with the (R)-(+)-O-vinyl-pantolactone does not lead to the expected dihydrooxazine, but to the corresponding tetrahydrooxazinone, as a result of the loss of the t-Bu group. A diastereoselective and asymmetrical way to these new heterocyclic compounds is described, together with the first evidence of their ability to undergo N-acylation.
作者:David S. Laitar、John W. Kramer、Bryan T. Whiting、Emil B. Lobkovsky、Geoffrey W. Coates
DOI:10.1039/b913698c
日期:——
4-Substituted oxazolines, which are readily synthesized from naturally occurring α-amino acids, are converted efficiently and stereospecifically to β-amidoaldehydes in the presence of synthesis gas and catalytic dicobalt octacarbonyl.
The asymmetricsynthesis of Maraviroc (UK‐427,857), a chemochine receptor 5 (CCR‐5) receptor antagonist, based on an expeditious organocatalytic enantioselective assembly of the chiral β‐amino aldehyde key fragment is presented. The reactions were performed on a gram‐scale and allow for the rapid construction of new Maraviroc analogues.
The first asymmetricorganocatalyzed one-pot α,α-bifunctionalization of acetaldehyde with two different electrophiles is described. A diarylprolinol silyl ether-catalyzed reaction of acetaldehyde with an imine and di-tert-butyl azodicarboxylate affords syn-2,3-diaminoalcohols with excellent ee values of up to 98%. This methodology was successfully applied to the synthesis of a chiral α,β-diaminocarboxylic
Novel Use of <i>N</i>-Benzoyl-<i>N,O</i>-acetals as <i>N</i>-Acylimine Equivalents in Asymmetric Heterocycloaddition: An Extended Enantioselective Pathway to β-Benzamido Aldehydes
For the first time, easily available N-(alpha-methoxyalkyl)amides were successfully used as synthetic equivalents of N-acylimines in an asymmetric heterocycloaddition process. The facial-controlled formation of 6-alkoxydihydrooxazines was thus achieved by SnCl4-promoted heterocycloaddition of (R)-O-vinyl pantolactone. By simple acidic hydrolysis of the crude heteroadducts, new beta-aryl- and beta-alkyl-substituted benzamido aldehydes were thus obtained in good overall yields with high enantioselectivities.