Chemistry

Academician of the Academy of Sciences of the Uzbek SSR A. S. Sadykov, Yu. K. Kushmuradov, and Kh. A. Aslanov

THE STRUCTURE OF ISOSOPHORAMINE

In studying the still residue accumulating in the production of pachycarpine from Sophora pachycarpa, we isolated a crystalline base, ( \mathrm{C}{15}\mathrm{H})), isolated from }\mathrm{ON}_2 ), m.p. (143—144^\circ), ([\alpha]_D = +52.86^\circ), (R_f = 0.46), which we named isosophoramine. Isosophoramine is a fairly strong tertiary monacidic base that gives crystalline salts (hydrochloride with m.p. (335—336^\circ) and picrate with m.p. (185—186^\circ)); in elemental composition isosophoramine is isomeric with anagyrine, thermopsine, sophoramine, and base No. 1 ((^{1-4Sophora pachycarpa, but in its properties it differs from the alkaloids listed above.

The absorption curve of isosophoramine in the ultraviolet region of the spectrum has two maxima ((\lambda_{\max} 309,\ 235\ \text{m}\mu)), lying in the ranges characteristic of lupine alkaloids containing an (\alpha)-pyridone ring in their molecule ((^5)). In the infrared absorption spectrum of isosophoramine there is a band characteristic of the lactam (> \mathrm{N—CO—}) group ((1623\ \text{cm}^{-1})). The lactam group of the base is stable toward acids and alkalis. The presence of double bonds in the (\alpha)-pyridone ring apparently imparts stability to the (> \mathrm{N—CO—}) group.

On hydrogenation of isosophoramine in the presence of Raney nickel, a tetrahydro derivative is formed (m.p. (104—105^\circ) from petroleum ether, ([\alpha]_D = +72^\circ), (R_f = 0.72); picrate with m.p. (179—181^\circ)), which in its constants resembles allomatrine ((^6)). The product of dehydrogenation of the tetrahydro derivative of isosophoramine with mercuric acetate likewise does not differ in its properties from 5-hydroxy-6,7-dehydromatrine, obtained by the indicated route from allomatrine ((^7)).

For final proof of the identity of tetrahydroisosophoramine with allomatrine, we obtained allomatrine by the known method ((^8)), i.e., by hydrogenating matrine in glacial acetic acid with a Pt catalyst. The allomatrine thus obtained gives no depression of the melting point in a mixed sample with tetrahydroisosophoramine. On the basis of the above data, we propose for isosophoramine the structure (I)

[structural formula]

(I)

To confirm the position of the double bonds in the isosophoramine molecule, we studied the reaction of oxidative cleavage of the latter with a quantity of chromic anhydride in 5% sulfuric acid calculated for two double bonds. In the reaction products it was possible to detect oxalic acid by paper chromatography, (R_f = 0.66) (n-butanol : (\mathrm{CH_3COOH}) : water, in the ratio (4 : 1 : 1)), which indicates conjugation of the double bonds in the isosophoramine molecule. Besides oxalic ac-

lute from the reaction mixture, after alkalinization with barium hydroxide hydrate, a base (C_{11}H_{18}ON_2) was isolated, m.p. (136—137^\circ) (from petroleum ether), (R_f = 0.53), ([\alpha]_D = +57.9^\circ) (in alcohol).

In the IR absorption spectrum of this base there is a band characteristic of the

[
\mathrm{H—N—CO—}
]

group and of the trans-quinolizidine nucleus ((^9)). On reduction of the substance (C_{11}H_{18}ON_2) with metallic sodium in boiling absolute alcohol, a base (C_{11}H_{20}N_2) was isolated, m.p. (90—91^\circ) (from petroleum ether), which is isomeric with 9-azohexahydrojulolidine ((^{10})), gives a dipicrate with m.p. (254—255^\circ) (from alcohol), and a dibromohydrate with m.p. (347—349^\circ) (from a mixture of alcohol and acetone). On dehydrogenation of (C_{11}H_{20}N_2) over 40% palladized asbestos in a stream of nitrogen at (230—270^\circ), a compound (C_{11}H_{14}N_2) was obtained, which in its physicochemical constants (see Table 1) and UV spectra is identical with 9-azojulolidine (IV) ((^{11})).

Table 1

Consequently, the compound (C_{11}H_{20}N_2) has the structure of 9-azohexahydrojulolidine (III), and the base (C_{11}H_{18}ON_2) has the structure of 9-azo-10-oxotetrahydrojulolidine (II)

[
\text{(II)}
\;\xrightarrow[\mathrm{Na + C_2H_5OH}]{\mathrm{H_2}}\;
\text{(III)}
\;\xrightarrow{\mathrm{Pd\text{-}asb}}\;
\text{(IV)}
]

The formation of 9-azo-10-oxotetrahydrojulolidine and oxalic acid on oxidation of isosophoramine indicates that the double bonds in its molecule are located at positions (C_{11-12}) and (C_{13-14}). The course of the oxidation of isosophoramine may be represented by the following scheme:

[
\text{isosophoramine}
\;\xrightarrow[\left(5\%\,\mathrm{H_2SO_4}\right)]{\mathrm{CrO_3}}\;
\mathrm{HOOC{-}COOH}
\;+\;
\left[\text{intermediate } \mathrm{N{-}CO{-}COOH}\text{ derivative}\right]
\;\xrightarrow{\mathrm{HOH}}\;
\text{9-azo-10-oxotetrahydrojulolidine}
]

Tashkent State University
named after V. I. Lenin

Received
23 II 1962

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