ISSN:
0170-2041
Keywords:
Azocino[4.3-b]indole, 1,5-methano-
;
Carbazoles
;
Hexahydrocarbazoles
;
Strychnos alkaloids
;
Alkaloids
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Synthesis of the Azocino[4.3-b]indole Core Structure of Strychnos AlkaloidsMichael addition of ethylmalonic dimethyl or diethyl ester with cyclohexenone and subsequent Fischer indole ring closure afford the (tetrahydrocarbazolyl)malonic esters 4a-c. Decarboxylation of 4a leads to the corresponding butyric acid methyl ester 5 which is oxidized by DDQ to the 4-oxo derivative 6a (byproduct: carbazole 7). Oximation of 6a to 8a and acylation of the oxime group to 8b, c as well as hydrogenation of this group yield 9a, b. Subsequent hydrogenation of the tetrahydrocarbazole ring by means of borane/pyridine yields the hexahydrocarbazole derivatives 10a and b. By cyclisation in boiling o-xylene (sodium hydride catalysis) 10a is converted into the tetracyclic 1,5-methanoazocino[4.3-b]indole derivative 11a with an alkaloid analogous ethyl side chain. The X-ray structural analysis of the corresponding phenylsulfonyl derivative 11b confirms constitution and stereochemistry. As a diastereoisomer of 11a the byproduct 11c could be isolated.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.1993199301115
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