BIOSYNTHESIS OF CINCHONA ALKALOIDS .2. INCORPORATION OF TRYPTOPHAN-1-15N,2-14C AND GERANIOL-3-14C INTO QUININE

The administration of DL-tryptophan-1-15N,2-14C (prepared from indole-1-15N,2-14C) to Cinchona succirubra plants yielded labeled quinine having all its 14C at C-9, and excess 15N only on the quinoline nitrogen. Furthermore, the specific incorporation of 14C and 15N into these positions was identical (0.97%). These results strongly support the hypothesis of Goutarel, Janot, Prelog, and Taylor, who suggested in 1950 that quinine and related quinoline alkaloids found in Cinchona species are derived from indole alkaloids of the corynantheine type. Additional evidence favoring this biosynthetic scheme was obtained by feeding geraniol-3-14C to the same species, when quinine labeled specifically at C-10 of the quinuclidine nucleus was obtained. This result is in agreement with recent work on the origin of the nontryptophan-derived portion of indole alkaloids containing an extra nine- or ten-carbon unit. © 1969, American Chemical Society. All rights reserved.