Carapanolides A and B: unusual 9,10-seco-mexicanolides having a 2R,9S-oxygen bridge from the seeds of Carapa guianensis

Two novel limonoids, named carapanolides A (1) and B (2) were isolated from the seeds of Carapa guianensis AUBLET (Meliaceae), a traditional medicine in Brazil and Latin American countries. Their structures elucidated on the basis of spectroscopic analyses using 1D and 2D NMR techniques were quite unusual, bearing 2,9-oxygen bridge in the 9,10-seco-mexicanolide skeleton. Compound 1 showed moderate activity against L1210 cell line.