Sceletium alkaloid

Dendrobium Alkaloids.—A third synthesis of shihunine, the principal base of several Dendrobium spp., has been reported. It involves allowing the dilithio-anion (12) to react with l-methyl-2-pyrrolidone (13), to yield ( )-shihunine (14) in 23% yield.11 Full experimental details pertaining to a synthesis of ( )-dendrobine, reported briefly earlier, have been described.12 

Fukushima, A. Ueno, T. Miyase, Y. Iitaka, and Y. Saiki, Chem. Pharm. Bull., 1979, 27, 1495. 

Stereoselective total syntheses of (-)-deoxoprosopinine (20) and (-)-deoxoprosophylline (21), derived respectively from the natural bases prosopinine and prosophylline, have been described the route adopted should be applicable to other related piperidine bases.20 Prosafrinine (22), a piperidine alkaloid of Prosopis africana, has been synthesized stereoselectively, along with pseudocar-pamic acid (23), as racemic varieties.21 Additional stereoselective syntheses of ( )-carpamic and ( )-azimic acids have been described.22 

Sceletium Alkaloids.—A new synthesis of (+)-mesembrine has been reported it uses a chiral y-lactone as a synthon. An alternative synthesis of ( )-sceletium alkaloid A4 has also been described.12 

Dendrobium Alkaloids. —An earlier reported synthetic route to (+)-dendrobine has been improved by the development of a superior synthesis of the perhydroindenone intermediate that is involved.13 

The structure of (—)-sedinine, an alkaloid of several Sedum spp., must be modified to (12), with the double-bond at C(3)-C(4) rather than at C(4)-C(5), as a consequence of X-ray diffraction analyses of the base and of its hydrochloride (12) also represents its absolute configuration.18 Sedacryptine is a new minor base from S. acre a single-crystal X-ray analysis of the free base points to structure and relative stereochemistry (13).19 The alkaloid could be identical with hydroxy-sedinone , isolated earlier.20 

The review mentioned earlier also includes some piperidine alkaloids.8 Pip lartine-dimer A, a dimer of the known alkaloid piplartine, has been isolated from the root bark of P. tuberculatum. Its structure and configuration, (14), have been settled by spectral study, and the compound has been synthesized by photochemical dimerization of piplartine (15).21 

Xylostosidine is a novel sulphur-containing monoterpenoid glucosidic alkaloid that occurs in the water-soluble extract of Lonicera xylosteum L. Its structure (17) has been elucidated by mass and n.m.r. spectroscopy.23 Two additional alkaloid glucosides, loxylostosidines A and B, have been isolated from the same source. They are the two geometrical isomers of xylostosidine sulphoxide, the former with a P S—O bond and the latter with an a, on n.m.r. spectral evidence.24 

namaquense its structure is based on spectral study Several new syntheses of meserabrine have been reported. One uses a cinna-monitrile as a synthon, with introduction of a formyl anion at the S-position, followed by Robinson annelation and finally elaboration of the cyanomethyl side-chainA second employs an intramolecular ene cyclisation of an acylnitroso-olefin to a hydroxamic acid, reducible to a lactam. Then follows a series of simple steps (N-methylation, hydroxylation via bromohydrin formation, debromi- 

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Scheme 11.29. Total synthesis of the Sceletium alkaloid (—)-mesembrine 112 [75],...

The H NMR spectrum of sceletium alkaloid A4, a tetracyclic system related to the octahydroindole members of the mesembrine alkaloids, is summarized in [152]. The close similarity of the 13C NMR spectra of... 

Sceletium Alkaloids.—Another synthesis of ( )-mesembrine has been described,9 and also the first total synthesis of (—)-mesembranone (ll),10 summarized in Scheme 1. 

Heating the 1,1 -disubstituted alkene with excess sarcosine ethyl ester in xylene with molecular sieves in a sealed tube at 180°C (7 h) afforded (60) (40%) (Equation (31)) <84JA7i75>. This product was then processed in two steps to (+ )-Sceletium alkaloid A4. 

A review entitled General Methods of Alkaloid Synthesis includes pyrrolidine, pyridine, and Sceletium alkaloids.1 Another summarizes nitrogen-containing compounds in tobacco and tobacco smoke, and includes some pyrroles, pyrrolidines, pyridines, and alkaloids related to nicotine.2... 

Sceletium Alkaloids.—(-)-Mesembrane has been isolated from S. namaquense L. Bolus X-ray diffraction analysis of its hydrochloride monohydrate revealed its relative and absolute configuration (10). (-)-Mesembrine has the absolute configuration (11), in accord with (10), and it is now firmly established that alkaloids of this family belong to a single antipodal series.13... 

The Sceletium alkaloid ( )-A4 (36) has been synthesized as shown in Scheme 5, using previously developed enamine-vinyl ketone ring annulation methodology (see Vol. 7 of these Reports).12 Treatment of the hydrochloride of the 2-pyrroline (32) with the acetal enone (33) gave a mixture of epimeric keto-acetals (34) in 85%... 

Confalone has successfully utilized the deprotonation route (Section II,D) for the synthesis of sceletium alkaloid A4 (84JA7175). Deprotonation of... 

Two total syntheses of sceletium alkaloid A4 (42) have been reported. The first, which involves a rearrangement of a cyclopropylimine to a pyrroline, is condensed in Scheme 12. The general pattern of the second (Scheme 13) is similar. ... 

The mood elevating properties of Sceletium tortuosum have been attributed to mesembrine [9], an alkaloid with potent selective serototun (5-HT) re-uptake inhibition activity 86). Other sceletium alkaloids as they are now referred to are mesembrenone, mesembrenol and tortuosamine. The use of mesembrine-type alkaloids was patented 92). Selective serotoiun (5-HT) re-uptake inhibitors (SSRls), like mesembrine, have become important treatments in the therapeutic management of depression 93). Several southern African medicinal plants, in particular Amaryllidaceae, have shown in vitro affinity for serotoiun re-uptake transporters 94,95). Several active alkaloids have been identified from Boophone and Crinum species 95, 96). 

The synthesis of mesembrine-type alkaloids belonging to the Sceletium alkaloid family has been carried out extensively in order to seek a... 

In order to prove the biosynthesis of the Sceletium alkaloids, an extensive study has been carried out using Sceletium subvelutinum L. Bolus that were grown from seed, and the six aUcaloids (447-452) (Fig. 26) produced by S. subvelutinum (101) isolated. These six alkaloids were separated chromato-... 

By means of labeled tracers and chemical degradations it was shown that the aromatic ring in the Sceletium alkaloids is derived from the aromatic ring of phenylalanine but not of tyrosine and that the per-hydroindole moiety is derived from tyrosine and not from phenylalanine. The S-methyl group of L-methionine provides the 0- and A-methyl groups 170). 

Fig. 1. Sceletium alkaloids isolated from Amaryllidaceae species...

Sceletium Alkaloids.—Full details of an earlier briefly reported synthesis of ( )-mesembrine (3) have been published and a new synthesis has been described. The latter is outlined in Scheme 1 A new Sceletium alkaloid has been isolated from S. namaquense. It has been formulated as (4) on spectral evidence, the assignment of structure being confirmed by direct spectral comparison between the natural base and racemic (4), synthesized earlier. Channaine, another alkaloid of this family, from S. tortuosum, has structure (5) on the basis of an X-ray diffraction analysis of its hexahydrate. It may be an artefact arising from the condensation of a pair of iV-desmethylmesembrenone molecules (6) during isolation. ... 

Sceletium Alkaloids.— The total synthesis of ( )-sceletium alkaloid A4 (10) has been described (Scheme 1). A parallel sequence afforded the 3 -demethoxy-alkaloid. ... 

Alkaloids of the group have been reviewed/ and an account of lactone alkaloids of the Amaryllidaceae has been published/ A concise account of recent developments in the synthesis of Amaryllidaceae alkaloids has appeared/ Contrary to previous practice, Sceletium alkaloids and related compounds are classified as pyrrolidine derivatives and discussed in Chapter 2. The Amaryllidaceae alkaloid cherylline is included in the account of isoquinoline alkaloids (Chapter 8). 

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