Whole-cell fermentation of o-halo methyl benzoates provided new cis-dihydrodiol metabolites.

Three new versions of the Burgess reagent were synthesized and their thermal stability investigated by NMR. The new reagents exhibited improved reactivity toward epoxides, diols, and vinyl oxiranes as compared with the original version.

As a means to circumvent the standard and sometimes troubling conjugate addition reaction of thiols to alkyl propiolates, a new reagent, cesium (Z)‐2‐carbomethoxyethenethiolate, is introduced. The cesium carbonate mediated methanolysis of (Z)‐2‐carbomethoxyethenyl thiolacetate at low temperature creates cesium (Z)‐2‐carbomethoxyethenethiolate in solution. For base‐insensitive and solvolytically stable electrophiles, efficient substitution can be achieved by direct introduction to the electrophile. The conditions were adapted to accommodate base‐sensitive cysteine derivatives, and the use of DMF as a cosolvent permits the isolation of (Z)‐2‐carbomethoxyethenyl cysteinyl thioethers in high enantiomeric purity (>99:1 er) and with good Z/E ratios. There was no evidence of carbon substitution reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Amino acids U 0400Cesium (Z)-2-Carbomethoxyethenethiolate: A Reagent for the Preparation of (Z)-2-Carbomethoxyethenyl Thioethers Including Selected Cysteine and Homocysteine Derivatives. -The cesium salt of the (Z)-enethiolate (III) is introduced as a new reagent for the synthesis of various 2-carbomethoxyethenyl thioethers. The (Z) stereochemistry is retained at low temperature. Secondary halides such as (IX) do not give the expected products. The reaction can be adapted to base-sensitive cysteine derivatives such as (XVII) and to homocysteine derivatives such as (XIX). In contrast, the direct addition of a thiol to methyl propiolate (I) leads to a complex mixture. -(O'DONNELL, J. S.; SINGH, S. P.; METCALF, T. A.; SCHWAN*, A. L.; Eur. J. Org. Chem. 2009, 4, 547-553; Dep. Chem., Univ. Guelph, Guelph, Ont. N1G 2W1, Can.; Eng.) -Kieslich 22-191