Catalytic Enantioselective Aldol Additions of α-Isothiocyanato Imides to Aldehydes
作者:Le Li、Eric G. Klauber、Daniel Seidel
DOI:10.1021/ja804838y
日期:2008.9.17
Highly enantioselective organocatalytic aldol additions of alpha-isothiocyanato imides to aldehydes are reported. These reactions provide convenient access to enantiomerically enriched and protected beta-hydroxy-alpha-amino acids with catalyst loadings as low as 1 mol%.
A novel process is described for preparation of biotin comprising preparation of substituted 3H, 5H-imidazo[1, 5c]tetrahydro thiazoles by contacting the boron trifluoride adduct of an appropriate thiazoline with the metallic derivative of an ester enolate, reducing the ester, hydrolyzing the thiazolidine moiety and hydrolyzing or oxidizing the resultant compound. Intermediates obtained in the preparation of biotin by the above process and alternate procedures for preparing said intermediates are also presented. A novel process for preparation of d-biotin is also given.