I. S. Nizamov, E. Nikitin, E. S. Batyeva
Jul 15, 2015
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Russian Journal of Organic Chemistry
Abstract
Natural compounds with asymmetric carbon atoms, in particular alkaloids, can be used as a source of chiral centers in their functionalization products. Promising synthons in the design of biologically active compounds are hydroxy-containing chiral alkaloids, such as quinine and cinchonine. Accessibility of these alkaloids has underlain their use as chiral P,N-bidentate ligands for metal complexes, catalysts for asymmetric syntheses, chromatographic selectors, and chiral NMR reagents [1–4]. Wide potential of their application for various purposes is determined by specific features of the molecular structure of quinine and cinchonine as major components of cinchona alkaloids, which consist of a quinoline fragment and vinyl-substituted bicyclic quinuclidine moiety with a tertiary nitrogen atom. Their molecules possess four chiral carbon atoms and one stereogenic nitrogen atom. Quinine alkaloids are represented by diastereoisomeric 8R,9S-quinidine and 8S,9R-quinine. Dithiophosphorylation products of quinine derivatives have not been reported so far. Dithiophosphates with quinine and cinchonidine fragments linked to the phosphorus through a sulfur atom have recently been synthesized by stereoselective functionalization of the corresponding O-methanesulfonyl derivatives with O,O-diethyl hydrogen phoshorodithioate in the presence of triethylamine [1]. In this work we used tetraphosphorus decasulfide P4S10 as dithiophosphorylating agent whose reaction with alcohols is a traditional method of synthesis of dithiophosphoric acid derivatives [5]. By reaction of P4S10 with quinine in benzene at 60°C (10 h) we obtained O,O-bis[(8S,9S)-quinin-9-yl] phosphorodithioate (2) which was isolated as inner ammonium salt. The P–{H} NMR spectrum of 2 in benzene contained two signals at δP 105.5 and 106.2 ppm at a ratio of 1 : 1. The downfield shift of the phosphorus signal from the region typical of dithiophosphoric acid derivatives (δP 83–86 ppm [6]) is likely to result from migration of the SH proton to the tertiary nitrogen atom of the quinuclidine fragment with formation of inner salt. In fact, compound 2 displayed in the IR spectrum (KBr) a broad absorption band at 3358 cm due to stretching vibrations of the N–H bond. In the ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 6, pp. 899–900. © Pleiades Publishing, Ltd., 2015. Original Russian Text © I.S. Nizamov, E.N. Nikitin, E.S. Batyeva, R.F. Faskhetdinov, R.A. Cherkasov, 2015, published in Zhurnal Organicheskoi Khimii, 2015, Vol. 51, No. 6, pp. 915–916.