Syntheses of (±)-α- and (±)- γ- Lycorane via a Stereocontrolled Organopalladium Route
1991 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 56, no 9, 2988-2993 p.Article in journal (Refereed) Published
Total syntheses of (+/-)-alpha-and (+/-)-gamma-lycorane are described. The key steps in the syntheses are the stereocontrolled palladium-catalyzed intramolecular 1,4-chloroamidation of 12 to 13 and the subsequent anti-stereoselective copper-catalyzed S(N)2' reaction of allylic chloride 13 with [3,4-(methylenedioxy)phenyl]magnesium bromide to give 14. Hexahydroindole 14 has the required relative stereochemistry between carbons 3a, 7, and 7a for alpha-lycorane (1a) and was transformed to the latter via 15 and 16. The epimeric gamma-lycorane (2) was obtained by performing the Bischler-Napieralski cyclization on 14, which led to a highly stereoselective isomerization to give exclusively 17. Compound 17 was subsequently transformed to 2. The overall yield from ester 8 to (+/-)-alpha- and (+/-)-gamma-lycorane was 40 and 36%, respectively.
Place, publisher, year, edition, pages
1991. Vol. 56, no 9, 2988-2993 p.
IdentifiersURN: urn:nbn:se:uu:diva-84527DOI: 10.1021/jo00009a011ISI: A1991FJ84000011OAI: oai:DiVA.org:uu-84527DiVA: diva2:112435