Process for the preparation of substituted derivatives of N-ethylglycine

摘要

Prepn. of N-ethyl-glycine derivs. of formula PG-X-CH2CH2-N(CO-B)-CH2COOH (I) or their salts, comprises: (a) reacting protected amino acid derivs. of formula RX-CH2CH2-NH-CH2COOR1 (II) with nucleo-base-acetic acid deriv. of formula B-CH2COOH (III) at 0-45 degrees C in a suitable solvent, and in the presence of a standard peptide coupling agent to give a cpd. of formula RX-CH2CH2-N(COCH2B)CH2COOR1 (IV); (b) removing the acid-labile ester protecting gp. from (IV) (where X = NH the protecting gp. R is also removed) under acid conditions in soln., opt. with addn. of a cation scavenger to give a cpd. of formula HX-CH2CH2N(COCH2B)CH2COOH (V) (when X = O, (IV) may also be treated with a base in an aq. medium); (c) reacting (V) with the appropriate reagent in soln. and in the presence of a base to give (I), and opt. converting to its salt. PG = amino protecting gp. labile in the presence of a weak acid of the urethane or trityl types; X = NH or O; B = standard nucleotide base in which exocyclic amino and OH gps. are protected conventionally; R = H or if X = NH, an acid-labile protecting gp.; and R1 = protecting gp. labile towards acid but stable towards amine. Also new are the intermediates (IV).