Quararibea Metabolites. 4.(1) Total Synthesis and Conformational Studies of (+/-)-Funebrine and (+/-)-Funebral.
Syntheses of racemic forms of the main secondary metabolites of Quararibea funebris, (+/-)-funebrine, (+/-)-funebral, and their biogenetic precursor (+/-)-(2S,3S,4R)-gamma-hydroxyalloisoluecine lactone have been developed. In synthetic studies, a new variation of the Paal-Knorr condensation employing titanium isopropoxide was utilized to construct the pyrrole lactone moiety. Two efficient synthetic approaches to the key (+/-)-gamma-amino lactone have been developed, one based on Claisen chemistry and the other on addition reactions to the butenolide ring of beta-angelicalactone. The restricted rotation around the C(sp(3))-N(sp(2)) bond in the pyrrole lactone structures of (+/-)-funebrine, (+/-)-funebral, and related aldehydes has been probed by conformational dynamic studies, and the barriers for interconversion between conformations have been measured by full NMR line-shape analysis. Molecular mechanics (MMX) and a (1)H-(1)H NOE study indicate a distinct preferred conformation for (+/-)-funebrine.
Dong
Ying
Y
Department of Chemistry and Barnett Institute, Northeastern University, Boston, Massachusetts 02115-5096.
Niranjan N Pai
Niranjan
N
Ablaza
Sheri L.
SL
Yu
Shao-Xia
SX
Bolvig
Simon
S
Forsyth
David A.
DA
Le Quesne
Philip W.
PW