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Isolated rabbit Clara cells and a transformed human bronchial epithelial cell line, BEAS-2B, were used to investigate the mechanism of cytotoxicity of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), a persistent insecticide and stable metabolite of 1,1,1-trichloro-2,2- bis(p-chlorophenyl)ethane. Both BEAS-2B cells and rabbit Clara cells were highly susceptible to DDD toxicity and were partially protected by 1-aminobenzotriazole, a suicide substrate inhibitor of cytochrome P450 enzymes. DDD (0.05 mM) killed 47 +/- 1.8% of rabbit Clara cells and 42 +/- 7.9% of BEAS-2B cells after 3 hr and 84 +/- 3.0% of rabbit Clara cells and 80 +/- 14% of BEAS-2B cells after 6 hr. Consequently, DDD is the most potent Clara cell toxicant recognized to date. The cytotoxicity of DDD to these cells was decreased by deuterium substitution at the C-1 position. Rabbit Clara cells and pulmonary microsomes incubated with 14C-DDD produced the fully oxidized acetic acid metabolite 2,2'-bis(p- chlorophenyl)acetic acid (DDA), but DDA was not formed by Clara cells when DDD was coincubated with 1-aminobenzotriazole. These results support the hypothesis that the cytotoxicity of DDD to susceptible subpopulations of rabbit and human lung cells is, at least in part, caused by cytochrome P450-mediated oxidation of DDD at C-1. A required step for the production of the cytotoxic intermediate is proposed to be the formation of a highly reactive acyl halide intermediate that is readily hydrolyzed to a stable, nontoxic metabolite, DDA.

Department of Chemistry, Government College, Sundergarh Manuscript received 4 April 1977, revised 7 September 1971. accepted 24 February 1978 A number of polymethin dyes derived from 6-methyl-phenaothridine as the fixed basic nucleus have been prepared and their absorption maxima data were determined. The absorption maxima data have been utilised for determination of relative basicities of different basic nuclei as well as for determination of relative acidities of different acidic nuclei. These dyes are expected to be good photographic sensitisers.

Government College, Sundargarh, Orissa Manuscript received 7 February 1979, revised 6 September 1979, accepted 9 January 1980 Polynuclear Photographic Sensitising Dyes Derived from 4-4' -p-Phenylene Bis-(2-Methyl Thiazole), Part-II.

Das D-Ribosederivat (I) reagiert mit (H) zu einem Gemisch der Phosphonate (III) und (IV), von denen (III) zur Titelverbindung (V) gespalten wird.

Department of Chemistry, Utkal University, Vani Vihar, Bhubaneswar-4, Orissa Manuscript received 13 March 1972; accepted 1974 A number of dimethin and tetramethin merocyanines derived from 2-methyl-4-(2'-thienyl and furyl) thiazoles have been prepared with a view to study the effect of these new heterocyclic substituents on absorption of the dyes.

A number of merocarbo and merodicarbo cyanines derived from 3-methyl benzo(f)quinoline as the fixed basic nucleus and (i) oxazolone, (ii) thiazolone, (iii) pyrazolone, (iv) thiobarbituric acid and (v) rhodanine as the variable acidic component are described. The deviations in their absorption maxima have been calculated and with the help of the deviation data, the relative acidities of the various acidic nuclei used have been determined. Sensitising properties of some of the above merocyanines have also been evaluated.

\(\beta\)-Diethylaminoacetoxy, \(\beta\)-amineothoxy, and \(\beta\)-diethylaminoethery derivatives have beenpreparedfrom hydroxyflavones. Some of them have been tested for their antispasmodic and antihistamine properties and found to pope activities comparable to standard compounds now used in practice.

Syntheses of Furo-Coumarins