The Corynane Group

19-Dehydroyohimbine, C2iH24N205 254 decomp. +106° (Py) Aspidosperma pyricollum MiiU.-Arg. 10 

Isovenenatine = alsto venine. 169-170 decomp. +9.42° Alstonia venenata 5, 6 

Ouroparine, C21H17N2O2 — — TJncaria gambier (Roxb.) Baillon 9 

Pioraphylline, C22H28N204 255 -37° (CHCI3) Picralima nitida Stapf 25 

Mitrajavine, C22H26N204-H20 117 -37.6° (CHCI3) M. javanica Koord et Valetone 19a 

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It has been possible to correlate yohimbine with the corynane group by opening ring E (5). The reduction product (XI) of yohimbone (IX) with sodium borohydride was converted as shown to the corresponding chloride (XII). Elimination of hydrogen chloride from this and oxidation of the unsaturated base (XIII) yielded a dialdehyde (XIV) whose bis-semicarbazone on reduction with hydrazine gave dihydrocorynantheane (XV), the absolute configuration of which had already been established (Vol. 7, p. 37). 

In this section are described the syntheses of some simple indolo-[2,3-a]quinolizine derivatives which bear a close relationship to the alkaloids of the yohimbane and corynane groups. 

Several syntheses of corynane derivatives have been reported in the recent literature. dZ-Corynantheine has been totally synthesized by van Tamelen s group (44) (Chart VI). The key intermediate, LXXIII, obtained by a biogenetic type of interaction of tryptamine, formaldehyde and the ketoester LXXII, was converted in four steps to an isomeric mixture (15,2.0- ra9 s/c s-isomers) of the tetracyclic ketoester LXXIVa,b. 

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