Benzyl Chloroformate Links

Since they already had a good synthesis of racemic ester, a late stage in the synthesis, an enzymatic hydrolysis looked a good bet. In the event hydrolysis with Candida antarctica lipase was superlative hydrolysis gave only the required enantiomer and stopped cleanly at 50% conversion. Various supported versions were tried and the best was the Boehringer L-2 preparation in which the enzyme is covalently bound to a cross-linked resin making it stable in aqueous solution. In the pilot plant 76 kgm of racemic methyl ester 230 react in 2.5 hours with 6 kg of supported enzyme. Benzyl chloroformate in CH2C12 is added and the unreacted ester (7 )-230,... 

An elegant approach for the preparation of secondary amines is outlined in Scheme 11. The method is based on the efficient cleavage of N-benzyl-linked tertiary amines from a solid support by treatment with a-chloroefhyl chloroformate/ methanol [30]. 

PMMA cross-linked by ethylene dimethacrylate with immobilized side oligooxy-ethylene chains were used as interfacial transfer catalysts [80]. Also studied was the formation of benzyl acetate, benzyl bromide and alkali metal acetates in boiling chloroform and of n-octylphenyl ester from n-octyl iodide and K or Na phenoxide in toluene at 100 °C in the presence of a catalytic polymer amount. The product yield increased with an increase in the reaction time and the catalyst/acetate or catalyst/ phenoxide molar ratio. The conversion of benzyl bromide increased according to the following sequence of acetates Napolymeric catalyst could be regenerated and used many times. 

Dichlorocarbene (generated in situ from chloroform) reacted with l,2 5,6-di-0-isopropylidene-a-D-glucofuranose in a phase-transfer system to give the rearranged product 6-chloro-6-deoxy-l,2 3,5-di-0-isopropylidene-a-D-glucofuranose, whereas 2,3 5,6-di-O-isopropylidene-a-D-mannofuranosyl chloride was obtained from the reaction of dichlorocarbene with 2,3 5,6-di-0-isopropylidene-a-D-manno-furanose. The a-D-mannofuranosyl chloride derivative was used to prepare the corresponding methyl and benzyl a-glycofuranosides and in the synthesis of a-linked disaccharide derivatives. 

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