Deracemisation of β-hydroxy esters using immobilised whole cells of Candida parapsilosis ATCC 7330: substrate specificity and mechanistic investigation
摘要:
Deracemisation of aryl substituted beta-hydroxy esters by immobilised whole cells of Candida parapsilosis ATCC 7330 gave > 99% ee and up to 75% yield of their corresponding (S)-enantiomers. Mechanistic investigation of the deracemisation reaction carried out using a deuterated substrate, ethyl 3-deutero-3-hydroxy-3-phenyl propanoate revealed that while the (S)-enantiomer remains unreacted the (R)enantiomer undergoes enantioselective oxidation to its corresponding ketoester, which on complementary enantiospecific reduction gives the (S)-enantiomer in high yield and % ee. (c) 2006 Elsevier Ltd. All rights reserved.
Potent mechanism-based inhibition of the TEM-1 .beta.-lactamase by novel N-sulfonyloxy .beta.-lactams
作者:Alexey Bulychev、Michael E. O'Brien、Irina Massova、Min Teng、Tracy A. Gibson、Marvin J. Miller、Shahriar Mobashery
DOI:10.1021/ja00127a005
日期:1995.6
A novel class of N-sulfonyloxy beta-lactam molecules are described as potent mechanism-based inactivators for the bacterial TEM-1 beta-lactamase, a prototypic class A enzyme. These molecules inactivate the enzyme with k(inact)/K-i values in the range of 1-7 x 10(4) M(-1) s(-1) and partition ratios (i.e., k(cat)/k(inact)) of 2-7. The mechanism of action of these inactivators was investigated. These molecules acylate the active-site serine of the TEM-1 beta-lactamase, a process that results in the release of the sulfonate attached to the lactam nitrogen, giving rise to a proposed beta-amino cinnamoyl derivative as the inhibitory species. This species undergoes gradual hydrolysis with concomitant recovery of activity, the rate constants for which were evaluated.
SCHAAL C.; RICARD M., J. LABELLED COMPOUNDS AND RADIOPHARM., 1979, 16 NO 5 727-733