DOPA DERIVATIVES

1347375 Phenylalanine derivatives F HOFFMANN-LA ROCHE & CO AG 29 Oct 1971 [30 Oct 1970] 50335/71 Heading C2C [Also in Division A5] Novel compounds of Formula I: wherein R 1 represents a hydroxy group or an alkoxy group which may be alkenyl-, alkynyl- or phenyl-substituted, R 2 represents a hydrogen atom, a phenyl group or an alkyl group which may be alkenyl- or alkynyl-substituted, R 3 represents a hydrogen atom, an alkanoyl group which may be substituted by alkoxy or by phenyl which may be alkoxy- or halo-substituted, a benzoyl group which may be alkoxy- or halo-substituted, an alkenoyl group, an alkynoyl group, an alkoxycarbonyl group which may be phenyl-substituted, an aminocarbonyl group which may be alkyl-substituted or a phenyl-thio group which may be nitro-substituted and R 4 represents an alkanoyl group which may be substituted by alkoxy or by phenyl which may be alkoxy- or halo-substituted, a benzoyl group which may be alkoxy- or halo-substituted, an alkenoyl group, an alkynoyl group, an alkoxycarbonyl group, an aminocarbonyl group which may be alkyl-substituted, an alkylsulphonyl group, an alkoxymethyl group or an alkyl group which is substituted by alkenyl, alkynyl, alkoxyalkyl, cyano, carboxy, alkoxycarbonyl (which may be alkenyl-, alkynyl- or phenylsubstituted) or aminocarbonyl (which may be alkyl-substituted) and wherein aliphatic groups R 1 to R 4 or aliphatic portions of the groups R 1 to R 4 each contain up to 18 carbon atoms, provided that R 3 has a significance different from R 4 , and with the proviso that when R 1 is hydroxy, R 2 is hydrogen, and R 3 is hydrogen or acetyl, R 4 is not acetyl, and salts thereof are prepared by one of the following methods: (a) a compound of formula wherein R 1 is a hydroxy group when R 3 represents a hydrogen atom, or a salt thereof, after protection of an -NHR 2 group which may be present by complex-formation with a copper (II) salt, with an agent furnishing the group R1 4 , wherein R1 4 has any of the values accorded to R 4 in claim 1 except carboxyalkyl, and cleaving a copper (II) complex with the aid of an acidic agent, or (b) esterifying a free acid of Formula I wherein R 1 is OH and R 4 is not alkoxymethyl or (c) subjecting an ester of formula wherein R 2 and R 3 have the significance given above, R1 1 has any of the values accorded to R 1 above except hydroxy and R111 4 represents an alkyl-sulphonyl group, an alkoxymethyl group or an alkyl group which is substituted by alkenyl, alkynyl, alkoxyalky