Titanium(IV)-Mediated Tandem Deprotection−Cyclodehydration of Protected Cysteine N-Amides: Biomimetic Syntheses of Thiazoline- and Thiazole-Containing Heterocycles
摘要:
[GRAPHICS]The scope and limitations of TiCl4-mediated Delta(2)-thiazoline synthesis via tandem deprotection-dehydrocyclization of trityl-protected cysteine N-amides is presented. While chemical yields are acceptable (53-96%), the stereochemical outcomes vary on the basis of structural considerations and reaction conditions (22-99% ee). Racemization at the C(2)-exomethine position limits the utility of this method for the formation of a thiazoline within a peptide. Treatment of a tritylated Cys-Cys dipeptide with TiCl4 afforded the corresponding thiazole-thiazoline heterocycle 12 (38% yield, 97% ee).
Titanium(IV)-Mediated Tandem Deprotection−Cyclodehydration of Protected Cysteine <i>N</i>-Amides: Biomimetic Syntheses of Thiazoline- and Thiazole-Containing Heterocycles
作者:Prakash Raman、Hossein Razavi、Jeffery W. Kelly
DOI:10.1021/ol000178q
日期:2000.10.1
[GRAPHICS]The scope and limitations of TiCl4-mediated Delta(2)-thiazoline synthesis via tandem deprotection-dehydrocyclization of trityl-protected cysteine N-amides is presented. While chemical yields are acceptable (53-96%), the stereochemical outcomes vary on the basis of structural considerations and reaction conditions (22-99% ee). Racemization at the C(2)-exomethine position limits the utility of this method for the formation of a thiazoline within a peptide. Treatment of a tritylated Cys-Cys dipeptide with TiCl4 afforded the corresponding thiazole-thiazoline heterocycle 12 (38% yield, 97% ee).
A Biomimetic Synthesis of Thiazolines Using Hexaphenyloxodiphosphonium Trifluoromethanesulfonate