Dihydrooxazole derivatives, synthesis

G. Fronza, C. Fuganti, A. Mele, and G. Pedrocchi-Fantoni, On the use of (4S,5S)-2-phenyl-4,5-dimethyl-4-formyl-4,5-dihydrooxazole in the synthesis of N-protected 2,3,4,6-tetradeoxy-4-C-methyl-4-amino-L-hexose derivatives, J. Carbohydr. Chem. 70 197 (1991). 

The synthesis starts from 2,4,4-trimethyl-4,5-dihydrooxazole, a compound with marked C—H acidity in the exocyclic methyl group. Triple lithiation followed by derivatiza-tion with chlorotrimethylsilane affords a triply silylated, open-chain ketenimine which is reacted with [AuCl(PPh3)] in the presence of caesium fluoride to give a dimeric, octanu-clear gold(I) cluster. The reaction proceeds beyond the stage of a triauriomethyl oxazolinyl derivative which, in fact, can only be observed as a side product. 

The derivative, silylated at both oxygens, 10 is named (S.S)-BISPAD13 and is also used for the preparation of dihydrooxazoles (Section D.1.1.1.2.). (S.S)-PAD denotes the 1,3-dioxane formed from the aminodiol and acetone13 which is used in the asymmetric Strecker synthesis. 

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