Amsonia

Among plumeran alkaloids isolated from the leaves of T. coffeoides (Hazunta modesta), two minor compounds were not previously discussed (70). One was recognized as 3-oxotabersonine (68, C21H22N203, MP 151.5-153°C, [a]D -11.4°) identical to the product isolated by Sakai from the seeds of Amsonia elliptica (198). Compound 68 was also obtained in 32% yield by KMn04 oxidation of tabersonine (67). 

The other antirhine iVb-metho salt, namely, antirhine Ab-(3-methochloride (13) has been isolated from Amsonia elliptica Roem. and Schult. (27). Demethylation... 

The enzyme responsible for the stereospecific condensation of trypt-amine and secologanin 34) was called strictosidine synthase, and its presence was demonstrated by Treimer and Zenk 194) in a number of indole alkaloid-producing plants, including Amsonia salicifolia, Catharanthus roseus, Ochrosia elliptica, Rauwolfia vomitoria, Rhazya orientalis, Stem-madenia tomentosa. Vinca minor, and Voacanga africana. Enzyme activity as high as 1698 pkat/mg protein was observed for O. elliptica. No... 

Tabersonine (XCII), an amorphous base which occurs in the seeds of Amsonia tabernaemontana (65, Volume VII, p. 134), in some Stem-madenia species (66, 66a), and in Tabernaemontana alba (66a), is a member of a distinct group of aspidospermine-type alkaloids which bear an extra carbon atom in the form of a carbomethoxyl group linked to position 3. The other members of this group are described briefly in Section II, P and in detail in Chapter 12. 

Tabersonine (108), clearly a reduced and simplified version of the second-half of the alkaloids 22, was originally isolated from Amsonia tabemaemontane L. and is considered to be a simplified parent of a rather more elaborate subgroup of indole alkaloids. 

Isolation of the stereospecific strictosidine s)mthase (STS) and formation of strictosidine with the 3a-(S) configuration proved conclusively that this was the natural precursor of the terpenoid indole alkaloids. Strictosidine occurs naturally in Rhazya stricta and the synthase has been isolated from a number of other species Amsonia salicifolia, A. tabemaemontam, Catharanthus pusillus, C. roseus, Rauvolfia verticillata, R. vomitoria, R. serpentina, Rhazya orientalis and Voacanga africana. The enzyme has been purified to homogeneity from R. serpentina (Hampp and Zenk, 1988). A comparison of the activity of STS from C. roseus roots, the only portion of the plant to contain ajmalicine, with that present in plant cell cultures producing the same alkaloid demonstrated that the plant cell cultures are far more metabolically active (Ziegler and Facchini, 2008). 

Aspidospermine-Aspidofractine-Eburnamine Group. The leaves of Pandaca minutiftora contain (+)-vincadifformine, which also occurs in the leaves of Amsonia tabernaemontana, together with ten other alkaloids [tabersonine, (+)-l,2-dehydroaspidospermidine, (—)-quebrachamine, lochnericine, ( ) and (—)-vincadine, (-)and ( )-epivincadine, (+)-14,15-dehydrovincadine, and (+)-14,15-dehydroepivincadine] the roots contain the first four alkaloids and ebumamonine. 

Tetrahydrosecamine occurs in Amsonia elliptica, and a diastereoisomer of (- )-5,6,5, 6 -tetrahydropresecamine mPandaca minutiflora. °... 

The Nb-oxide of tabersonine (78) is reported to occur in the seeds of Amsonia elliptica Roem. et Schult. (101), in which it is accompanied by 3-oxotabersonine (107). Four other sources of 3-oxotabersonine have also been recorded (15,93,103,109). The structure of this alkaloid was established (101) by hydrogenation to 3-oxovincadifformine, which was identified by comparison with a (racemic) synthetic sample (1), and by its preparation by oxidation of tabersonine by means of potassium permanganate (101). 

Epoxy -16 - hydroxy -16 - methoxycarbony 1 - 3 - oxo -1,2- didehydro-aspidospermidine (127) has been extracted from the seeds of Amsonia elliptica (101). However, this is almost certainly an artifact, derived by aerial oxidation of 3-oxotabersonine (107), which occurs in the same plant, or its epoxide. 

Monoterpenoid Alkaloids.—Corynantheine-Heteroyohimbine-Yohimbine Group, and Related Oxindoles. The first recorded extraction of the leaves and twigs of Peschiera laeta Mart, has yielded geissoschizol, a base not previously found in the Peschiera genus. Antirhine and, to a lesser extent, its quaternary Nb-metho-derivative, occur in the bark of Strychnos camptoneura Gilg. et Busse and in Amsonia elliptica, which also contains tetrahydrosecamine, pleiocarpamine,... 

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