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The structure of mappicine, a minor alkaloid isolated from Mdppia foetida Miers. has been established as ( I I a ) (7-(1 -hydroxypropyl)-8-methylindolizino[l.2-b]quinolin-9(11 H)-one) by partial synthesis from camptothecin Centre, Goregaon, Bombay 400 063, India (W.WE have previously reported the isolation of the antitumour alkaloid camptothecin (Ia) from Mappia foetida Miers (family; Olacaceae) . l s 2 A new alkaloid isolated from the plant was shown to be 9-methoxycamptothecin (Ib) by spectral studies. T.1.c. examination of the mother liquors of crystallisation of these alkaloids showed the presence of traces of more polar compounds with green or blue U.V. fluorescence. By repeated chromatography of this material over silica gel we have isolated 1 T. R. Govindachari and N. Viswanathan, Indian J . Chsm., 1972, 10, 463.one new alkaloid in very small yield. This has been named mappicine and we now report evidence leato structure (IIa) for the alkaloid.Mappicine, C1,Hl,N2O2 (M+ 306), has a U.V. spectrum closely resembling that of camptothecin (Ia). Its i.r. spectrum shows bands a t 3380, 3280 (OH), 1660, and 1590 cm-f (pyridone) but lacks the a-lactone peak at 1745 cm-1 which is present in camptothecin. Acetylation of mappicine gives a monoacetate. The n.m.r.

The frequent occurrence of the isoquinoline nucleus in alkaloids has led to considerable interest in the synthesis of isoquinolone derivatives. Many methods have been developed, but only three have enjoyed popularity. One of them, the Bischler‐Napieralski reaction is discussed in this chapter. The reaction consists in the cyclodehydration of beta‐phenethylamides to 3,4‐dihydroisoquinolines by heating to high temperatures with phosphorus pentoxide or anhydrous zinc chloride. Yields were not given for the original reaction, but later studies proved that the yields were low. Modifications using lower temperatures and milder condensing agents improved the reaction. The most important variation was introduced by Picet and Gams, which eliminates the dehydrogenation step. The classical synthesis of papaverine by Pictet and Gams is discussed.

The Pictet‐Spengler reaction, in its simplest form, consists in the condensation of a beta‐arylethylamine with a carbonyl compound to yield a tetrahydroisoquinolone and is a special example of the Mannich reaction. The condensation of phenethylamine with methylal in concentrated hydrochloric acid to form 1,2,3,4‐tetrahydroisoquinoline was achieved in 1911 by Pictet and Spengler. Their reaction has been applied to the synthesis of other ring systems. The theory that proteins are the parent substances of alkaloids was tested by Pictet, who heated casein with methylal and hydrochloric acid, obtaining a mixture of pyridine and isoquinoline bases. Most of the products were not definitely identified.

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