Cassane diterpenoids of Caesalpinia pulcherrima

Five new cassane diterpenoids (1-5) were isolated from the roots of Caesalpinia pulcherrima, along with the known isovouacapenol C (6), pulcherrimin A (11), and 6beta-cinnamoyl-7beta-hydroxyvouacapen-5alpha-ol (12). Compounds 3-5 possess the alpha,beta-butenolide moiety, whereas compounds 1 and 2 contain a more usual 2,3-disubstituted furan unit. Compounds 7 and 8 were derived from hydrolysis of 6, while 9 and 10 were derived from acetylation and oxidation of 6, respectively. The H-1 and C-13 NMR spectra of all compounds were completely assigned using a combination of 2D NMR. experiments, including H-1-H-1 COSY, HSQC, HMBC, and T-ROESY sequences.