Dihydroindole alkaloids

Because of the previous inaccurate botanical determination of the Madagascan periwinkle, the alkaloids of this plant were formerly considered as Vinca alkaloids, an erroneous subclassification for alkaloids isolated from a plant belonging to the genus Catharanthus. It also should be noted that the alkaloids of C. roseus containing two different (most commonly indole and dihydroindole) alkaloid building blocks were, and sometimes still are, referred to as dimeric indole alkaloids. It is more accurate to use the term binary or bisindole alkaloids, since chemically these alkaloids are not dimers of two equal subunits, but rather comprised of two (bis) different alkaloid building blocks. 

N. Neuss, Physical Data of Indole and Dihydroindole Alkaloids, 4th rev. ed., Vol. II. Lilly, Indianapolis, Indiana, 1962. 

Transannular cyclization. In a recent total synthesis of indole and dihydroindole alkaloids,3 a key step is a transannular cyclization reaction with mercuric acetate. For example, the reaction of 4/3-dihydrocleavamine (1) with mercuric acetate yields the indolenine (2), which was isolated as the more stable reduction product (3). 

Three dihydroindole alkaloids isolated from Kopsia officinalis... 

The basic fraction of the root bark of Tabemaemontana amygdalifolia Sieber ex A. DC. gave two dihydroindole alkaloids (60), the structures of which were deduced mainly on the basis of mass spectrometry. 

The mass spectrum of henningsoline did not show the peaks at m/e 144 and 130, characteristic of unsubstituted dihydroindole alkaloids. However, intense peaks at m/e 190 and 176 (144 and 130 plus 46 replacement of H by OH and H by OMe = 46 mass units) indicated a substituted dihydroindole structure. 

Kasturi (1963) has presented some infrared data concerning alkaloids. Among the compounds were quinozilidine alkaloids, methyl neoreserpate, 3-epialloyo-himbone, and 3-epialloyohimbine (conformational data). Other compounds mentioned were the tobacco alkaloid myosmine the substances histisine, angustifoline, recanescine, and reserpine other Rauwolfia alkaloids some Vinca alkaloids and powellane. Neuss (1959) has also supplied data on indole and dihydroindole alkaloids. 

Kutney, J. P., T. Hibino, E. Jahngen, T. Okutani, A. H. Rat-cliffe, a. M. Treasurywala, and S. Wunderly, Total synthesis of indole and dihydroindole alkaloids. IX. Studies on the synthesis of bisindole alkaloids in the vinblastine-vincristine... 

It is noteworthy that -seco indole alkaloids appear only in the leaves and stems, whereas dihydroindole alkaloids occur in the roots. Possible biosynthetic interrelationships of these isolated alkaloids are proposed in Fig. 5.2.16. 

J.P. Kutney, F. Bylsma, Total synthesis of indole and dihydroindole alkaloids. VII. The total synthesis of isovelbanamine, velbanamine, cleav-amine, 18p-carbomethoxycleavamine and catharanthine, Helv. Chim. Acta 58 (1975) 1672-1689. 

Kutney JP, Abdurahman N, Gletsos C, Quesne PL, Piers E, Vlattas I. Total synthesis of indole and dihydroindole alkaloids. V. Total synthesis of dl-quehrachamine and dl-aspidospermidine. General entry into the aspidosperma alkaloids. J. Am. Chem. Soc. 1970 92(6) 1727-1735. 

---