Polycyano-substituted carbo- and heterocycles that we synthesized earlier possessed antitumor properties [1]. High antitumor activity for compounds with hydroxyl, methoxyl, methoxycarbonyl, and cyano groups would be predicted from the literature [2,3,4,5,6].

Methyl-6-amino-3-acyl-4-aryl-5-cyano-4H-pyran-2-carb oxylates (I) were prepared by reacting 2-arylidenemalononitriles with methyl-2,4-dioxobutanoates [7]. 9-Aryl-12-imino-10,11-dioxatricyclo[5.3.2.01, 6]dodecane-7,8,8-tricarb onitriles (II) were synthesized from cyclohexanone tetracyanoethylene adduct and aldehydes by the usual method [8]. Reactions of cyclohexanone tetracyanoethylene adducts with 1,3,5-tri-substituted 2,4-diazapenta-1,4-dienes by the literature method [9] gave 1,2,5,6,7,8-hexahydroquinoline-3,3,4,4-tetracarbonitriles (III).

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Antiproliferative activity of cyano-substituted I-III was studied at the National Cancer Institute (USA) using an in vitro model that allowed the experimental conditions to be standardized for repetitive series according to the NCI-60 One-Dose Screen protocol [10]. The studies used 60 tumor cell lines [11] from human lung, colon, brain, ovary, kidney, prostate, breast, leukemia, and melanoma. Results were processed statistically using the Student t-criterion. An effect was considered statistically significant for p < 0.05. It was found that IIIa [2-(4-methoxyphenyl)-1,2,5,6,7,8-hexahydroquinoline-3,3,4,4-tetracarbonitrile] had the most promising antiproliferative activity for further research (Table 1). IIIa at a concentration of 10–5 M showed significant inhibition of tumor cell growth.

Table 1 Antiproliferative Activity of Compounds (10–5 M) (from One-Dose Screen Program)
Full size table

The test results showed that substituted tetracarbonitrile IIIa was most active against leukemia cell lines because it suppressed considerably growth of all test cultures [CCRF-CEM, HL-60(TB), K-562, MOLT-4, RPMI-8226, SR]. The average inhibition of these cell lines was 74.91%; maximum, 98.88% (SR).

Thus, substituted tetracarbonitrile IIIa at a concentration of 10–5 M was much more active than known antitumor preparations such as busulfan and cisplatin.

The high alkylating capability of cyano groups with respect to various nucleophiles [12, 13] suggested that the antiproliferative activity of the compounds could be due to cyanoalkylation of nucleophilic sites on tumor-cell DNA molecules. Furthermore, the steric positioning of the cyano groups in the ethyl-1,1,2,2-tetracarbonitrile moiety is favorable for rapid coordination to nucleophilic sites, which accelerates the cyanoalkylation.

The results confirmed our hypothesis that the ethyl-1,1,2,2-tetracarbonitrile moiety in the cyclic compounds was a pharmacophore.