Studies on synthesis and anticancer activity of selected N-(2-fluoroethyl)-N-nitrosoureas.

An activated carbamate, 2-nitrophenyl (2-fluoroethyl)nitrosocarbamate (3), was used to advantage in the synthesis of the water-soluble (2-fluoroethyl)nitrosoureas 6a--d from 2-aminoethanol, (1 alpha, 2 beta, 3 alpha)-2-amino-1,3-cyclohexanediol, cis-2-hydroxycyclohexanol, and 2-amino-2-deoxy-D-glucose. In a variation of this method, 2,4,5-trichlorophenyl (2-fluoroethyl)carbamate (4) was used to prepare the urea from which the essentially water-insoluble N-(2,6-dioxo-3-piperidinyl)-N-(2-fluoroethyl)-N-nitrosourea (6e) was derived. The anticancer activity of these nitrosoureas was determined against the murine tumors B16 melanoma and Lewis lung carcinoma and found to be significant and comparable to their chloroethyl counterparts. On the basis of results from both systems, the dihydroxycyclohexyl derivative 6b may be the most effective.

New anticancer agents: synthesis of 1,2-dihydropyrido[3,4-b]pyrazines (1-deaza-7,8-dihydropteridines).

Reaction of alpha-aminoacetophenone oximes (2) with ethyl 6-amino-4-chloro-5-nitropyridine-2-carbamate (1) gave ethyl 6-amino-5-nitro-4-[(2-oxo-2-phenylethyl)amino]pyridine-2-carbamate oximes (3), which were hydrolyzed under acidic conditions to give the corresponding ketones (4). Related pyridines substituted with a keto side chain were prepared from 1 and 1,3-diaminopropanone oximes and by oxidation of the side-chain hydroxy group of ethyl 6-amino-4- [[3-(N-methyl-N-phenylamino)-2-hydroxypropyl]amino]-5-nitropyridine-7- carbamates (6). Catalytic hydrogenation of the nitro group of 4 over Raney nickel in a large volume of ethanol gave the 1-deaza-7,8-dihydropteridines (7). Several of the oximes 3 were successfully hydrogenated to give 7 directly. The resulting 1-deaza-7,8-dihydropteridines showed potent cytotoxicity against cultured L1210 cells and significant anticancer activity against lymphocytic leukemia P-388 in mice. These biological activities are attributed to the accumulation of cells at mitosis.

New synthesis of N-[4-[[(2-amino-4(3H)-oxopyrido[3,2-d]pyrimidin-6-yl)methyl]amino]benzoyl]-L-glutamic acid (8-deazafolic acid) and the preparation of some 5,6,7,8-tetrahydro derivatives.

Previously, 8-deazafolic acid (17) was shown to be a potent inhibitor of the folate-dependent bacteria, Streptococcus faecium (ATCC 8043) and Lactobacillus casei (ATCC 7469), and to have activity against lymphoid leukemia L1210 in mice. To examine the 5,6,7,8-tetrahydro derivatives, a new synthesis of 17 was developed from 8-deaza-2,4-dichloro-6-methylpteridine. Treatment of the latter with aqueous base gave the corresponding pteridin-4(3H)-one, which was aminated with ammonia to give 8-deaza-6-methylpterin (9). Bromination of 9 gave mainly 8-deaza-6-(tribromomethyl)pterin, which on reaction with p-aminobenzoyl-L-glutamic acid resulted in the formation of the 9-oxo derivative of 17. In contrast, bromination of the 2-acetyl derivative of 9 gave mainly the corresponding 6-(bromomethyl)pterin, which was converted to 17 in 23% yield (from 9). Hydrogenation of 17 at atmospheric pressure and room temperature was unsuccessful either in a basic medium or formic acid. In trifluoroacetic acid, overreduction occurred to give a mixture containing 8-deaza-5,6,7,8-tetrahydro-6-methylpterin and the 5,6,7,8-tetrahydro derivative of 17. The latter was characterized by conversion to the methenyl analogue 21, which was also prepared by hydrogenation of the 10-formyl derivative of 17. Treatment of 21 with hydroxide gave 8-deaza-10-formyl-5,6,7,8-tetrahydrofolic acid. Compound 21 showed cytotoxicity to cultured H.Ep.-2 cells and was tested as an inhibitor of bovine dihydrofolic reductase. Lineweaver-Burk analysis indicated inhibition competitive with dihydrofolate.

Synthesis of some glycoside analogs and related compounds from 9-amino-6-(methylthio)-9H-purine.

Additional information on the anticancer activity of 9-amino-9H-purine-6(1H)-thione and its derivatives was sought by the synthesis of some 9-(substituted amino)-6-(methylthio)-9H-purines in which the 9-substituent contained functional groups capable of either reversible or irreversible binding with an enzymatic site. Condensation of 9-amino-6-(methylthio)-9H-purine (1) with some carbonyl compounds followed by hydride reduction of the azomethine linkage in the intermediates leads to the 2-pyrrolylmethyl (8), 2,3,4-trihydroxybutyl (10), and the 1,5-dihydroxy-2- and 3-pentyl (11 and 12) compounds. A 4-hydroxybutyl derivative (13) was obtained by alkylation of 18, the 9-acetyl derivative of 1, with 4-chlorobutyl acetate followed by saponification. The cyclization of 13 and 11 with a sulfonyl chloride gave the 9-pyrrolidin-1-yl (27) and the 9-[2-(tosyloxymethyl)pyrrolidin-1-yl] (28), respectively. Acylation of 1 with ethyl L-2-pyrrolidine-5-carboxylate and ethyl 1-methyl-5-pyrrolidone-3-carboxylate, respectively, in Me2SO containing NaH gave the corresponding amides 15 and 17. Alkylation of 18 with 1-bromo-2-chloroethane and epichlorohydrin gave the N-(2-chloroethyl) and N-(1,2-epoxy-3-propyl) derivatives 19 and 20. The chloro group of the chlorobutyl derivative of 18 was displaced with KSCN and NaN3, respectively, to give the thiocyanate and azido derivatives 23 and 24. Hydrogenation of the latter gave the amine (25), which was acylated with ethyl chloroformate to give the (ethoxycarbonyl)amino compound 26. None of these compounds showed activity against L1210 leukemia cells implanted ip in mice on a single-dose schedule, suggesting that the activity observed in the simpler 9-aminopurines resulted from cleavage of the hydrazino linkage to give pH-purine-6(1H)-thione.