Adriamycin analogues. rationale, synthesis, and preliminary antitumor evaluation of highly active DNA-nonbinding N-(trifluoroacetyl)adriamycin 14-O-hemiester derivatives.

N-(Trifluoroacetyl)adriamycin 14-valerate (AD 32), a novel DNA nonbinding analogue of adriamycin with superior experimental antitumor activity, has undergone extensive clinical trial, with documentation of antitumor activity and low toxicity in human subjects. However, poor water solubility necessitates that the drug be administered to patients by continuous intravenous infusion at high dilution in a surfactant-containing formulation, with steroid prophylaxis to protect against a chest pain syndrome associated with the vehicle. On the basis of pharmacologic considerations, the title compounds have been prepared as second-generation analogues of N-(trifluoroacetyl)adriamycin 14-valerate with improved aqueous solubility; use is made of the available carboxylic acid function to solubilize the products in dilute aqueous alkaline medium. Target compounds were made by treating N-(trifluoroacetyl)-14-halodaunorubicin (bromo or iodo) with monosodium salts of dibasic acids (malonic, succinic, glutaric, adipic, pimelic, azelaic, sebacic) in aqueous acetone. All of the products showed significant in vivo antitumor activity against the murine P388 leukemia (ip tumor, ip treatment once daily on days 1, 2, 3, and 4); most compounds were superior to the +181% increase in life span afforded by adriamycin (optimal dose 3.0 mg/kg per day), one of two drugs used as positive controls for the assays. Several of the test compounds showed highly curative activity in this system, similar to N-(trifluoroacetyl)adriamycin 14-valerate, the other positive control agent. The hemiadipate product exhibited the most desirable properties of high antitumor efficacy (86% cure rate all P388 tumor-bearing animals through four levels of a 40-70 mg/kg dose-response range), aqueous solubility (60 mg/mL in pH 7.4 phosphate buffer), and solution stability (no decomposition at 4 degrees C, 0.5% hydrolysis at 27 degrees C, over 24 h at pH 7.4).

4-Halovinyl- and 4-ethynyl-4-deformylpyridoxal derivatives and related analogues as potentially irreversible antagonists of vitamin B6.

Analogues of pyridoxal bearing alpha- and beta-chlorovinyl, beta-bromovinyl, butadienyl, acetyl, and 1-butenyl groups in place of the formyl group have been synthesized by subjecting 3,alpha5-di-O-benzylpyridoxal to appropriate Wittig or Grignard reactions. Similar methods yielded one-carbon homologues of pyridoxal and pyridoxol. Synthesis of the 4-ethynyl analogue of pyridoxal was achieved by dehalogenating blocked beta-halovinyl derivatives. The substituted vinyl and the ethynyl analogues were found to be active as inhibitors of mouse mammary adenocarcinoma cells grown in cell culture at an ID50 of 10(-5)-10(-6) M. The inhibitory activity of the 4-ethynyl analogue could be partially reversed by pyridoxal. This analogue was found to inhibit pyridoxal phosphokinase, and its 5'-phosphate was likewise found to be a potent noncompetitive inhibitor of pyridoxine-P oxidase.

Antagonists of vitamin B6. Simultaneous and stepwise modification of the 2 and 4 positions.

Methods for the simultaneous and stepwise modification of the 2 and 4 positions of vitamin B6 have been devloped and have been applied to the synthesis of several analogues of this vitamin. 3,alpha5-O-Dibenzylpyridoxol was converted to its N-oxide and was rearranged to an alpha2-hydroxy derivative with (CF3CO)2O. The 2,4-bis(hydroxymethyl) intermediate was oxidized (MnO2) to the 2,4-dialdehyde, which was converted by a Wittig reaction with triphenylmethylphosphorane to the 2,4-divinyl derivative. Removal of the benzyl groups with acid gave the 2,4-divinylpyridioxol analogue, which was phosphorylated in the 5' position to give the cofactor analogue. The 2-CH3 in the known vitamin B6 antagonists, 4-deoxypyridoxol and 4-vinylpyridoxal, was similarly modified to CH2OH, CHO, and CH = CH2. Modifications of the 2 position in the vitamin B6 antagonists are expected to be associated with changes in selectivity for enzymes in various tissues without a concomitant loss of biological activity, because of the well-established bulk tolerance in this position. Active analogues are expected to undergo, in vivo 5-phosphorylation, which is probably a prerequisite for their antagonist activity. Some of the compounds (e.g., the 2,4-divinyl analogue) have substantial growth-inhibitory activity for cultured mouse mammary adenocarcinoma. In contrast to that of the parent compounds, this activity was only partially reversed by pyridoxal.

On the inhibitory activity of 4-vinyl analogues of pyridoxal: enzyme and cell culture studies.

Analogues of pyridoxal and of pyridoxal phosphate in which the 4-CHO group is replaced with CH = CH2 were synthesized and were found to be potent inhibitors of pyridoxal kinase and pyridoxine phosphate oxidase of rat liver. They also inhibited the growth of mouse Sarcoma 180 and mammary adenocarcinoma TA3 in cell culture. Saturation of the vinyl double bond, replacement of the 5-CH2OH with methyl, methylation of the phenolic hydroxyl, or conversion to the N-oxide resulted in diminution or loss of all these activities. Similarly, the introduction of a beta-methyl group into the vinyl analogues of pyridoxal reduced all these inhibitory activities. The 4-vinyl anatogue of pyridoxal was shown to be a substrate of pyridoxal kinase and the product a potent inhibitor of pyridoxine oxidase, competing with pyridoxal phosphate. The affinity of this phosphorylated pyridoxal analogue to some apoenzymes varied greatly, indicating striking differences among the cofactor binding sites of these enzymes. The growth inhibitory effects of these analogues on cells in culture correlated well with their effects on pyridoxal kinase and pyridoxine phosphate oxidase in cell-free systems.

Synthesis and biological properties of 4-amino- and 4-bromo-4-norpyridoxol. New approaches for the modification of the 4 position of vitamin B6.

4-Amino-4-norpyridoxol, a new key intermediate for the modification of the 4 position of vitamin B6, has been obtained by an unusual photochemical rearrangement of pyridoxal oxime. It has also been synthesized starting from 3,-alpha5-O-dibenzylpyridoxal, which was converted to 3,alpha5-O-dibenzylpyridoxamide. The latter, on Hoffman reaction, gave the desired 3,5-blocked 4-amino derivative. Several derivatives of this analogue have been prepared, and its existence in the amino tautomeric form has been established by NMR spectroscopy. A modified Sandmeyer reaction on 4-amino-4-norpyridoxol gave the 4-bromo analogue, which was found to be moderately active as an inhibitor of mouse mammary adenocarcinoma cells grown in cell culture, whereas the 4-amino analogue was not active at 10(-4)M. Other analogues containing electron-withdrawing and electron-donating substituents in the 4 position of pyridoxine were also tested.