1) The condensation of 2,4,5,6-tetraaminopyrimidine sulfate (I) with dihydroxyacetone dimer (II) in the presence of cysteine and O2 furnished 2,4-diamino-6-(hydroxymethyl)pteridine (III). Subsequent reaction of (III) with dibromotriphenylphosphorane in dimethylacetamide afforded bromide (IV) which, without isolation, was condensed with 4-aminobenzoic acid (V) in the presence of BaO to give 4-amino-4-deoxypteroic acid (VI). Formylation of (VI) with acetic-formic anhydride yielded formamide (VII), and subsequent activation as the 4-nitrophenyl ester (IX) was carried out upon reaction with bis(4-nitrophenyl)carbonate (VIII). Then Nd-Boc-L-ornithine, after conversion to the corresponding Na,O-bis(trimethylsilyl) derivative (X) by treatment with ClSiMe3 and triethylamine, was condensed with active ester (IX) to furnish amide (XI). Subsequent deprotection of the Boc group of (XI) with cold trifluoroacetic acid provided (XII), which was then condensed with phthalic anhydride (XIII) in the presence of triethylamine in N-methylpyrrolidinone, yielding the hemiphthaloyl amide (XIV). Finally, the formamide function was hydrolyzed with aqueous NaOH at r.t. to provide the target compound, after chromatographic separation of some phthaloyl-hydrolyzed byproduct.

2) Alternatively, N10-formyl-4-amino-4-deoxypteroic acid (VII), prepared as before, was converted to the mixed anhydride (XV) with isobutyl chloroformate and triethylamine, and subsequently condensed with the Na,O-bis(trimethylsilyl) derivative of Nd-phthaloyl-L-ornithine (XVI) to give amide (XVII). Then, hydrolysis of the formamide function and concomitant phthalimide ring opening with aqueous NaOH provided the target compound.

1) The condensation of 2,4,5,6-tetraaminopyrimidine sulfate (I) with dihydroxyacetone dimer (II) in the presence of cysteine and O2 furnished 2,4-diamino-6-(hydroxymethyl)pteridine (III). Subsequent reaction of (III) with dibromotriphenylphosphorane in dimethylacetamide afforded bromide (IV) which, without isolation, was condensed with 4-aminobenzoic acid (V) in the presence of BaO to give 4-amino-4-deoxypteroic acid (VI). Formylation of (VI) with acetic-formic anhydride yielded formamide (VII), and subsequent activation as the 4-nitrophenyl ester (IX) was carried out upon reaction with bis(4-nitrophenyl)carbonate (VIII). Then Nd-Boc-L-ornithine, after conversion to the corresponding Na,O-bis(trimethylsilyl) derivative (X) by treatment with ClSiMe3 and triethylamine, was condensed with active ester (IX) to furnish amide (XI). Subsequent deprotection of the Boc group of (XI) with cold trifluoroacetic acid provided (XII), which was then condensed with phthalic anhydride (XIII) in the presence of triethylamine in N-methylpyrrolidinone, yielding the hemiphthaloyl amide (XIV). Finally, the formamide function was hydrolyzed with aqueous NaOH at r.t. to provide the target compound, after chromatographic separation of some phthaloyl-hydrolyzed byproduct.

2) Alternatively, N10-formyl-4-amino-4-deoxypteroic acid (VII), prepared as before, was converted to the mixed anhydride (XV) with isobutyl chloroformate and triethylamine, and subsequently condensed with the Na,O-bis(trimethylsilyl) derivative of Nd-phthaloyl-L-ornithine (XVI) to give amide (XVII). Then, hydrolysis of the formamide function and concomitant phthalimide ring opening with aqueous NaOH provided the target compound.

1) The condensation of 2,4,5,6-tetraaminopyrimidine sulfate (I) with dihydroxyacetone dimer (II) in the presence of cysteine and O2 furnished 2,4-diamino-6-(hydroxymethyl)pteridine (III). Subsequent reaction of (III) with dibromotriphenylphosphorane in dimethylacetamide afforded bromide (IV) which, without isolation, was condensed with 4-aminobenzoic acid (V) in the presence of BaO to give 4-amino-4-deoxypteroic acid (VI). Formylation of (VI) with acetic-formic anhydride yielded formamide (VII), and subsequent activation as the 4-nitrophenyl ester (IX) was carried out upon reaction with bis(4-nitrophenyl)carbonate (VIII). Then Nd-Boc-L-ornithine, after conversion to the corresponding Na,O-bis(trimethylsilyl) derivative (X) by treatment with ClSiMe3 and triethylamine, was condensed with active ester (IX) to furnish amide (XI). Subsequent deprotection of the Boc group of (XI) with cold trifluoroacetic acid provided (XII), which was then condensed with phthalic anhydride (XIII) in the presence of triethylamine in N-methylpyrrolidinone, yielding the hemiphthaloyl amide (XIV). Finally, the formamide function was hydrolyzed with aqueous NaOH at r.t. to provide the target compound, after chromatographic separation of some phthaloyl-hydrolyzed byproduct.

2) Alternatively, N10-formyl-4-amino-4-deoxypteroic acid (VII), prepared as before, was converted to the mixed anhydride (XV) with isobutyl chloroformate and triethylamine, and subsequently condensed with the Na,O-bis(trimethylsilyl) derivative of Nd-phthaloyl-L-ornithine (XVI) to give amide (XVII). Then, hydrolysis of the formamide function and concomitant phthalimide ring opening with aqueous NaOH provided the target compound.