Bromination of the acetals 4 derived from aryl alkyl ketones, ArCOR, and (2R,3R)-tartaric acid results in bromoacetals 5 with 78-90% de. Hydrolysis of those compounds with Ar = 4-methoxyphenyl or 3-bromo-4methoxyphenyl results, after recrystallisation, in α-bromoketones 8 with 66-98% ee which are shown to undergo the Baeyer-Villiger oxidation to α-bromoesters 9 with minimal racemisation. α-Bromoketone 8d is shown to undergo carbonyl reduction to threo-bromohydrin 15 with retention of stereochemistry.

2000 stereochemistry stereochemistry (general, optical resolution) O 0030 -029Enantioselective Synthesis of α-Bromo Acid Derivatives and Bromohydrins from Tartrate Derived Bromoacetals.-Bromination of optically active acetals (I) give in most cases products which can be recrystallized to stereochemical purity. α-Bromoketones (IIIc)-(IIIe), derived from the corresponding bromoacetals by hydrolysis, undergo Baeyer-Villiger oxidation to afford α-bromoesters (IV) with minimal racemization as is assessed by conversion to esters (VI) or amides (VIII). Ketone (IIc) is reduced to bromohydrin (IX) with retention of stereochemistry. -(BOYES, SCOTT A.; HEWSON, ALAN T.; Perkin 1 (2000) 16, 2759-2765; Div. Chem., Sheffield Hallam Univ., Sheffield S1 1WB, UK; EN)

Synthesis of Some Substituted Oxaspiro [4,5]decanenones by Way of Intermolecular Diels-Alder Reaction of Alkylidene 2,3-Dimethoxybutenolides Obtained from L-Ascorbic Acid.-The butenolide (Va), obtained from L-ascorbic acid (I), is treated with diester (VII) in order to obtain spirolactone (VI), a skeleton incorporated in several natural products. However, intramolecular cycloaddition of (Va) is observed instead forming the title compounds (VIII) and (IX) with the endo isomer as the main product. - (KHAN, M. A.; BOYES, S. A.; ADAMS, H.; Molecules 1 (1996) 27-36; Div. Chem., Health Res. Inst., Sheffield Hallam Univ., Sheffield S1 1WB, UK; EN)