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Improved approach for anchoring N alpha-9-fluorenylmethyloxycarbonylamino acids as p-alkoxybenzyl esters in solid-phase peptide synthesis.

Several Fmoc-amino acids have been esterified by use of N,N-dimethylformamide dineopentyl acetal to 2,4,5-trichlorophenyl 3'-(4''-hydroxymethyl-phenoxy)propionate, and the resultant handle derivatives were purified and then quantitatively coupled onto aminomethyl supports. Compared to literature methodology, the present procedure is preferred because: (i) extra steps to selectively protect and liberate the carboxyl of the handle are circumvented; and (ii) the additional methylene group spacer reflecting substitution of a propionyl group for an acetyl group in the handle changes the electronic parameters of the resultant p-alkoxybenzyl ester sufficiently so that the rates of acidolytic cleavage of the anchoring linkage are 2- to 3-fold increased and useful improvements in yields can be achieved.