1-Hydroxyethyl /3-carboline

Marine bryozoans and hydroids also contain /3-carboline alkaloids. (5)-l-(l -hydroxyethyl)- -carboline (176) was obtained from the Tas-... 

Danieli et al. 116), both of which utilize an alkylation process of 1-methyl-3,4-dihydro-(3-carboline (150) in the key ring-forming step. In the first one, treatment of 150 with a-methylene- y-butyrolactone gave enamide 172, which, when reduced with lithium aluminum hydride, afforded indolo[2,3-a]quinolizine derivative 173. The desired ethylidene substituent at C-20 has been developed from the hydroxyethyl side chain in a four-step sequence as shown below. 

The root bark of Ailanthus altissima Swingle contains the known alkaloids canthin-6-one (22), l-methoxycanthin-6-one, canthin-6-one A-oxide, and 1-acetyl-4-methoxy-/ -carboline, together with three new alkaloids, identified as 1-methoxy-canthin-6-one A-oxide, l-(2-hydroxyethyl)-4-methoxy-/ -carboline, and 1(1,2-dihydroxyethyl)-4-methoxy-/ -carboline.21... 

Starting from L-tryptophan, immobilized on hydroxyethyl polystyrene through its carboxylic group, the intermediate a,[3-unsaturated imine (554) was formed by reaction with 3-methylcrotonaldehyde in pure trimethyl orthoformate (TMOF). The imine was then allowed to react with Fmoc chloride in the presence of pyridine to afford the required tetrahydro-[3-carboline (555) through an N-acylimin-ium ion mediated Pictet-Spengler-type cyclization. Further manipulation of the Pictet-Spengler product afforded the desired demethoxy-FTC as the minor cis isomer, along with its C-3 trans epimer (556) (diastereoisomeric ratio 1 3) (Scheme 115). 

Scheme 17. Hannan [1], 1-ethyl-p-carboline [2], S-l-(l -hydroxyethyl)-P-carboline [3], and pavet-tine [4] from the bryozoan Costaticella hastata. 1-Acetyl-P-carboline [5] are known from Arenaria kansuensis.

The P-carboline alkaloids harman [1] and pavettine [4] from the bryozoan Costaticella hastata (207) are known from numerous terrestrial plants. Still another bryozoan compound (S)-1-(l -hydroxyethyl)- P-carboline [3] is new but closely related to 1-ethyl-P-carboline [2] present in the bryozoan. It is also known from the roots of Hannoa klaineana (Simaroubaceae) (208) and 1-acetyl-P-carboline [5] from Arenaria kansuensis (Caryophyllaceae) (209). Incidentally, pavettine [4] was detected in only one collection of the bryozoan. 

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