Carboline, 1-methoxycarbonyl

A Pd-catalyzed alkoxycarbonylation of 2-chloropyridine 117 to ester 118 was reported in the synthesis of camptothecin analogs <97JOC6588>. Another Pd-catalyzed alkoxycarbonylation was the central feature in Hibino s total synthesis of oxopropaline G (121), a P-carboline isolated from Streptomyces sp G324 <98TL2341>. Triflate 119 was prepared from 2-foimyl-3-iodoindole in seven steps. The Pd-catalyzed alkoxycarbonylation of 119 provided the key intermediate, l-methoxycarbonyl-4-methylcarboline 120, which was then transformed to oxopropaline G (121) in four additional steps. 

Acetyl-3-methoxycarbonyl-/ -carboline, the alkaloid of Vestia lycioides, has been synthesized by two routes 200,6 the second involves the benzylic oxidation-dehydrogenation of l-ethyl-3-methoxycarbonyl-l,2,3,4-tetrahydro-/ -carboline by means of selenium dioxide in dioxan. A by-product in this oxidation was 1 -acetyl-/ -carboline, which occurs in Ailanthus malabarica. An extension of this reaction led to a simple two-stage synthesis of canthin-6-one (22) from Ab-benzyltryptamine and a-ketoglutaric acid (Scheme 2).206... 

Norisotuboflavine (21) has been synthesised from canthinone " (22) and from l-methoxycarbonyl-)5-carboline (23) (Scheme 2). 

The factors that control diastereoselection in the construction of 1,3-disubstituted tetrahydro-p-car-bolines are not, as yet, well understood. With many aldehydes a slight preference for forming the trans diastereomer is observed. " This preference is somewhat greater when the indole nitrogen (Na) of the tryptamine is alkylated. Pictet-Spengler cyclizations of Nb-benzyltryptophan methyl ester under Cook s aprotic conditions are reported to provide nearly exclusively the rr 2ni-A b-benzyl-3-methoxycarbonyl-1 -substituted-1,2,3,4-tetrahydro-P-carbolines. ... 

VIII) may be briefly summarized as follows. Villalstonine is a dimeric, diacidic base, which contains one methoxycarbonyl group, two methyl-imino groups, and an ethylidene group. Its UV spectrum is consistent with the presence of indole and dihydroindole chromophores containing no substituents in the benzene rings. Alkali fusion yields 2-methylindole, indole 2-carboxylic acid, and a /3-carboline derivative selenium dehydrogenation also affords a j8-carboline derivative, so far unidentified. Acid hydrolysis of villalstonine yields pleiocarpamine (XV), one of the alkaloids of Pleiocarpa mutica Benth. 

Non-isoprenoid Tryptamines. The stems of Picrasma ailanthoides, from which plant canthine derivatives had previously been obtained, has now yielded 1-methoxycarbonyl- and l-hydroxymethyl-j5-carboline. The molecular shape of eserine (= physostigmine) in the crystal has been determined. The new evidence fits in well with information, summarized previously, from n.m.r. NOE measurements. More alkylations at the C-1 methyl of harmaline have been reported.The A -methyl derivative of 1,2,3,4,6,7,12,12b-octahydro-indolo[2,3-a]quinolizine has been isolated from cranberries. 

The new alkaloids of this group, all from Pleiocarpa species, are tubo-flavine (I) from Pleiocarpa tubicina Stapf [P. pycnantha. (K. Schum.) Stapf var. tubicina (Stapf) Pichon], the same alkaloid, isotuboflavine (II) (mp 263°-265°) and norisotuboflavine (III) (mp 282°-284°) from Pleiocarpa mutica Benth. l-Methoxycarbonyl-(8-carboline was also isolated along with the latter alkaloids (3). 

The isolation of a new jS-carboline alkaloid, l-acetyl-3-methoxycarbonyl-j8-carboline (10), from the leaves of Vestia lycioides Willd., constitutes the first reported occurrence of a /8-carboline derivative in the family Solanaceae. Several simple jS-carboline derivatives also occur in the bark and roots of Ailanthus malabarica DC. (fam. Simaroubaceae) these include 1-methoxy-carbonyl-j8 -carboline, 4-methoxy-1 -vinyl-/3 -carboline (dehydrocrenatine),... 

Anhydroalstonatine, a new alkaloid from the bark of Alstonia venenata, is a bright red, zwitterionic indolic base which is tentatively formulated as (101), i.e. as a 9-methoxy-5,6-dehydro-neo-oxygambirtannine. In consonance with this structure, reduction of anhydroalstonatine by means of sodium borohydride gave a tetrahydro-/3-carboline base, regarded as (102) the positions of the methoxy and methoxycarbonyl groups in (101) and (102) are based principally on the presence of two ABX systems of aromatic protons in the n.m.r. spectra of both compounds, and on the u.v. absorption of (102). 

Cl5H18N2O2, trans-l-Ethyl-3-(methoxycarbonyl)-1,2,3,4-tetrahydro-j3-carboline, 46B, 274... 

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