Phosphonate analogs of chorismic acid: synthesis and evaluation as mechanism-based inactivators of chorismate mutase
作者:Harold B. Wood、Hans Peter Buser、Bruce Ganem
DOI:10.1021/jo00027a034
日期:1992.1
The mechanism of chorismate mutase, the enzyme which catalyzes the Claisen arrangement of chorismic to prephenic acid, remains a fascinating area for bioorganic research. This paper describes the enantioselective synthesis of phosphonochorismic acids 3 and 4, two potential mechanism-based mutase inactivators, utilizing new transition-metal-catalyzed insertion reactions of tetraalkyl diazophosphonates. Models establish that such systems undergo smooth Claisen rearrangement and that the product acylphosphonates are good acylating agents for amines and alcohols. By contrast, thermolysis of phosphonochorismates 3 and 4 in the presence of enzyme led to p-hydroxybenzoic acid, with no trace of [3,3] rearrangement to the corresponding prephenates or phenylpyruvates. The half-life for elimination of 3 was 8.3 h (75-degrees-C, 2:1 CD3OD/D2O) while for 4 the half-life was 4.3 h. When tested over a wide range of concentrations against the E. coli chorismate mutases (so-called T- and P-proteins), neither 3 nor 4 interacted with the enzyme, either as a competitive inhibitor or as a substrate, perhaps reflecting the stringent demands of the rearrangment transition state. Earlier studies strongly suggest that the enol pyruvate carboxyl group is markedly tilted against the carbocyclic ring during [3,3] sigmatropy, and similar flattening of the tetrahedral phosphonate could create unfavorable steric as well as pi-pi interactions.