Potential inhibitors of nucleotide biosynthesis. 2. Halomethyl ketone derivatives of pyrimidine nucleosides.

Several halomethyl ketone derivatives of pyrimidine nucleosides have been prepared for evaluation as cytotoxic agents. The first series are 1-(8-halo-2,5,6,8- tetradeoxy -beta-D-erythro-oct-7 - ulofuranosyl )thymines (7-9), whereas the second type are halo derivatives of acetophenone (12-14 and 16). These compounds are cytotoxic, and one (13) showed activity against the P388 leukemia in vivo.

cis-4-[[[(2-Chloroethyl)nitrosoamino]carbonyl]methylamino] cyclohexanecarboxylic acid, a nitrosourea with latent activity against an experimental solid tumor.

cis-4-[[[(2-Chloroethyl)nitrosoamino]carbonyl]methylamino] cyclohexanecarboxylic acid (N-Me-cis-CCCNU) was synthesized in five steps from cis-4-aminocyclohexanecarboxylic acid via an N-tosylated intermediate. N-Me-cis-CCCNU, which is incapable of the facile decomposition that characterizes the clinically useful nitrosoureas, effected a significant cure rate of both early and established murine Lewis lung carcinoma, even though its in vitro half-life was approximately 5.5 times that of the unmethylated parent compound. This is the first observation of latent activity of a nitrosourea against an experimental solid tumor.

Synthesis of potential anticancer agents. Pyrido[4,3-b][1,4]oxazines and pyrido[4,3-b][1,4]thiazines.

Hydrolysis of the chloro group of ethyl (6-amino-4-chloro-5-nitropyridin-2-yl)carbamate (3) with formic acid gave the corresponding 4-hydroxypyridine 4. Catalytic hydrogenation of the nitro group of 4 gave the 5-amino-4-hydroxypyridine 5, which was reacted with alpha-halo ketones in acetic acid at room temperature to give a series of 3- and 2,3-substituted ethyl (5-amino-2H-pyrido[4,3-b][1,4]oxazin-7-yl)carbamates 8. Treatment of 8 with hot concentrated hydrochloric acid regenerated the pyridine synthon 5. In the reaction of 3 with thioacetate, the product underwent hydrolysis and air-oxidation to give the corresponding disulfide 6. Simultaneous reduction of both the nitro group and disulfide linkage of 6 gave the 5-amino-4-mercaptopyridine 7, which was reacted with alpha-halo ketones either in acetic acid at room temperature or in a mixture of ethanol and water at reflux to give a series of 3-, 2,3-, and 2,2,3-substituted ethyl (5-amino-2H-pyridol[4,3-b][1,4]thiazin-7-yl)carbamates 9. The effects of these pyridooxazines and pyridothiazines upon the proliferation and the mitotic index of cultured L1210 cells and upon the survival of mice bearing P388 leukemia were determined.

Synthesis and biological evaluation of 2-fluoro-8-azaadenosine and related compounds.

The synthesis of 2-fluoro-8-azaadenosine (6e) and 2-amino-8-azaadenosine (6d) is described. Condensation of 9H-2,6-bis(methylthio)-8-azapurine (4) with 2,3,5-tri-O-acetyl-D-ribofuranosyl chloride (5) produces a mixture of 6a (9-beta-D-ribofuranosyl) and 7a (8-beta-D-ribofuranosyl). Standard functional group manipulation, including a modified Schiemann reaction to introduce the fluorine, allows preparation of 6d and 6e from the major isomer 6a. By a similar series of reactions the minor component 7a was converted to 7d and 7e, with the ribose ring attached at N-8 of the 8-azapurine ring system. Structure proofs utilized UV and 1H and 13C NMR data. Compounds 6b-e,g and 7b-f were evaluated in the H.Ep.-2 cell culture screen, and compounds 6c-e and 7d were evaluated in the P388 mouse leukemia screen. Adenosine deaminase data are also presented for some compounds.

Has the well gone dry? The First Cain Memorial Award Lecture.

Contrary to a recent suggestion, new and useful drugs for the treatment of human cancer continue to be developed although clinical trials today are more difficult and the chances for success are diminished. In the past, research at Southern Research Institute led to the development of two new classes of clinically useful anticancer agents, the nitrosoureas and the imidazole triazines. More recently, we have developed an interesting family of cytotoxic compounds, the haloadenine nucleosides, that are resistant to deamination and show biological activity comparable to the corresponding adenine nucleosides given in combination with 2'-deoxycoformycin, a potent inhibitor of adenosine deaminase. Among them, the 2-haloadenine arabinonucleosides and 2'-deoxyribonucleosides appear to have the necessary selectivity for neoplastic cells to be useful anticancer agents.

Experimental studies at Southern Research Institute with DTIC (NSC-45388).

Several years ago the diazotization of 5-aminoimidazole-4-carboxamide was found to give an internal diazonium salt, 5-diazoimidazole-4-carboxamide, which demonstrated marginal activity against some murine neoplasms. In an effort to improve this activity and develop a clinically useful agent, this compound was converted to a number of derivatives including DTIC, an agent that showed encouraging activity against a variety of rodent neoplasms. Studies carried out at Southern Research Institute on the chemistry, metabolism, and biologic activity of DTIC and its congeners are discussed briefly.