The copper-salt promoted 1,4-additions of aryl and t-butyl Grignard reagents to ethyl 2,3-dideoxy-4,5:6,7-di-O-isopropylidene-~-arabino-trans-hept-2-enonate are highly stereoselective yielding products with the D-manno-configuration. In contrast isopropyl and ethyl Grignard reagents give products preponderantly with the D-gluco-configuration. Cyclohexylmagnesium bromide does not react stereoselectively but gives a 55 : 45 mixture of the D -~~U C O -and D-manno-isomers. Controlled degradation of the carbohydrate molecule affords 2-aryl (alkyl) butane-I ,4-dioic acids and 3-aryl (alkyl) -butyro-I ,4lactones. The enantiomeric purity of these products is established by reference to known products or by use of optically active n.m.r. shift reagents.
One of a new class of organometallic compounds, gold ketenide has an unusual structure and interesting properties. Gold films formed by its controlled thermal decomposition show possibilities as highly active and selective oxidation catalysts.
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