Hydro-de-phosphoniation of 4-substituted-4-triphenylphosphonio-5(4H)-oxazolones with alcohols

4-Substituted-4-triphenylphosphonio-5(4H)-oxazolones with a bulky alkyl sub stituent at the position 4 treated with McOH in the presence of DBU (1,8-di azobicyclo[5.4.0]undec-7-ene) at room temperature give corresponding N-acyl -alpha -amino acid esters. In the case of a smaller substituent at the posi tion 4 (Me, MeOCH2), the triphenylphosphonium group was competitively displ aced by the methoxy group. The latter reaction can be avoided by carrying o ut hydro-de-phosphoniation in CH2Cl2 in the presence of only 150% excess of i-PrOH at 50 degreesC in the absence of DBU. Possible mechanisms of hydro- de-phosphoniation are discussed.