Approach to the homoerythrina alkaloids using a tandem N-alkylation/azomethine ylide cycloaddition.
Synthetic efforts toward the homoerythrina alkaloids 1-3 are described. Two separate model systems guided the pivotal [3 + 2] azomethine ylide cycloaddition cascade to form the A-C rings of these alkaloids. The cycloaddition precursors 63 and 68, prepared in nine and ten steps, respectively, from alkyne 47, each contain an enolizable ketone, a tethered electrophile, and an electron-poor dipolarophile. Heating 63 and 68 with the stannyl amine 17 generated demethoxyschelhammeridine 65 and demethoxyschelhammericine 70, the products of intramolecular azomethine ylide cycloadditions. Subsequent attempts to install the C-3 methoxy group of 1-3 are also described.
Pearson
William H
WH
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA. wpearson@berryassoc.com
Kropf
Jeffrey E
JE
Choy
Allison L
AL
Lee
Ill Young
IY
Kampf
Jeff W
JW
D000470:Alkaloids / Q000138:chemical synthesis / Q000737:chemistry*; D000478:Alkylation; D000588:Amines / Q000737:chemistry; D001391:Azo Compounds / Q000737:chemistry*; D003500:Cyclization; D006576:Heterocyclic Compounds, 4 or More Rings / Q000138:chemical synthesis / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry; D015394:Molecular Structure; D010946:Plants, Medicinal / Q000737:chemistry; D013882:Thiosemicarbazones / Q000737:chemistry*
D000470:Alkaloids; D000588:Amines; D001391:Azo Compounds; D006576:Heterocyclic Compounds, 4 or More Rings; D007659:Ketones; D013882:Thiosemicarbazones; C512188:azomethine