NOVELTY - Preparing pralatrexate (I) comprises e.g. (a) alkylating dimethyl 2,2'-(1,4-phenylene)diacetate (II) with an alkylating agent in the presence of a base and phase transfer catalyst to obtain methyl 2-(4-(2-methoxy-2-oxoethyl)phenyl)pent-4-ynoate (III), and (b) coupling (III) with 6-bromomethyl-pteridine-2,4-diamine (IV) or its acid addition salt in presence of a base and a solvent to obtain a compound, which is treated with an acid to give 2-(2,4-diamino-pteridin-6-ylmethyl)-2-(4-methoxycarbonylmethyl-phenyl)-pent-4-ynoic acid methyl ester (V).    USE - The process is useful for preparing pralatrexate (claimed) which is used for treating cancer. No biological data given.    ADVANTAGE - The process: is a simple, convenient, economical and industrially viable commercial process; restricts the use of hazardous and expensive reagents and solvents; utilizes a simple and less laborious purification method; and restricts the use of expensive column chromatography, thus resulting in the formation of pralatrexate in high yields and with pharmacopoeial grade having improved purity.    DETAILED DESCRIPTION - Preparing pralatrexate of formula (I) comprises: (a) alkylating dimethyl 2,2'-(1,4-phenylene)diacetate of formula (II) with an alkylating agent in the presence of a base and phase transfer catalyst to obtain methyl 2-(4-(2-methoxy-2-oxoethyl)phenyl)pent-4-ynoate of formula (III); (b) coupling (III) with 6-bromomethyl-pteridine-2,4-diamine of formula (IV) or its acid addition salt in presence of a base and a solvent to obtain a compound, which is treated with an acid to give 2-(2,4-diamino-pteridin-6-ylmethyl)-2-(4-methoxycarbonylmethyl-phenyl)-pent-4-ynoic acid methyl ester of formula (V); (c) treating (V) with a base to give 2-(4-(carboxymethyl)phenyl)-2-((2,4-diaminopteridin-6-yl)methyl)pent-4-ynoic acid of formula (VI); (d) optionally converting (VI) to 3-(4-carboxymethyl-phenyl)-3-(2,4-diamino-pteridin-6-ylmethyl)-hex-5-ynoic acid of formula (VII), by treatment with a base, (e) decarboxylation of (VI) or (VII) by heating in a solvent to obtain a compound, which is treated with a base to give substituted 2-(4-(1-(2,4-diamino-pteridin-6-ylmethyl)-but-3-ynyl)-phenyl)-acetoxy compounds of formula (VIII); (f) optionally purifying (VIII) with a solvent or mixture of solvents; (g) coupling (VIII) with substituted (S)-(2-amino-5-(oxy)-5-oxopentanoyloxy) compounds of formula (IX) in the presence of a dehydrating agent and activating agent to give substituted (4S)-5-(oxy)-4-(2-(4-(1-(2,4-diaminopteridin-6-yl)pent-4-yn-2-yl)phenyl)acetoxyamino)-5-oxopentanoyloxy compounds of formula (X); and hydrolyzing (X) in presence of a base to give (I).    X1a = acid;    Y1a = base;    n = 1 or 2, preferably 2;    M1a = alkali metal; and    R1a = 1-4C alkyl.    INDEPENDENT CLAIMS are also included for:    (1) 2-(2,4-diamino-pteridin-6-ylmethyl)-2-(4-methoxycarbonylmethyl-phenyl)-pent-4-ynoic acid methyl ester (V);    (2) 3-(4-carboxymethyl-phenyl)-3-(2,4-diamino-pteridin-6-ylmethyl)-hex-5-ynoic acid (VII);    (3) substituted 2-(4-(1-(2,4-diamino-pteridin-6-ylmethyl)-but-3-ynyl)-phenyl)-acetoxy compounds (VIII);    (4) obtaining pure pralatrexate (I) comprising (a1) contacting pralatrexate with a mixture of alcohol and halogenated hydrocarbon to obtain a mixture, (b1) stirring the mixture at ambient temperature, (c1) collecting the solid, (d1) contacting the solid of step (c1) with demineralized water to obtain a mixture, (e1) stifling the mixture of step (d1) at ambient temperature, and (f1) isolating the pure pralatrexate; and    (5) pure pralatrexate (I).