Enantiomeric resolution of cyclobutanones and related derivatives by enzyme-catalyzed acylation and hydrolysis
作者:Reza Salezadeh-Asl、Edward Lee-Ruff
DOI:10.1016/j.tetasy.2005.10.043
日期:2005.12
A method for the regio- and enantioselective protection and deprotection of a number of cyclobutanone derivatives employing the isolated enzyme porcine pancreatic lipase (PPL) has been developed. PPL catalyzes the regioselective acylation or deacylation of the C-3 substituent in (2S,3R)-(+)-bis[hydroxymethyl]-1,1-dimethoxycyclobutanone and its enantiomer. Photochemical ring expansion of the corresponding cyclobutanones in methanol gave anomeric mixtures of the methyl furanosides with stereochemical retention of the ring substituents. The PPL-catalyzed hydrolysis of the acetal derived from (2S,3R)-bis[acetoxymethyl]cyclobutanone resulted in a regioselective reaction of the C-3 acetoxymethyl group. PPL exhibits no hydrolysis activity toward the acetal derived from the enantiomeric cyclobutanone diacetate.Racemic 2-acetoxymethyl-3,3-dimethylcyclobutanone was converted to its enantiomerically enriched (S)-alcohol by PPL-catalyzed hydrolysis. The corresponding methyl furanoside obtained from the photochemical ring expansion of racemic 2-acetoxymethyl-3,3-dimethylcyclobutanone in methanol is not an effective substrate for PPL mediated hydrolysis. (c) 2005 Elsevier Ltd. All rights reserved.
Synthesis of fluorocyclobutanones and their use in the synthesis of fluoronucleosides
作者:Hedieh Ghazi、Edward Lee-Ruff
DOI:10.1016/j.jfluchem.2005.09.007
日期:2005.12
Fluorocyclobutanones can be prepared from reaction of hydroxycyclobutanones with diethylaminosulfur trifluoride (DAST). Other fluorine containing cyclobutanones can be prepared by alkene/fluoroketene cycloadditions. The photochemical ring-opening of these synthetic intermediates with 6-chloropurine produces fluorinated nucleoside analogs. (c) 2005 Elsevier B.V. All rights reserved.