Yt. Ge et al., ABSOLUTE-CONFIGURATION OF NOVEL MARINE DITERPENOID UDOTEATRIAL HYDRATE SYNTHESIS AND CYTOTOXICITIES OF ENT-UDOTEATRIAL HYDRATE AND ITS ANALOGS, Tetrahedron, 49(46), 1993, pp. 10555-10576
Antipode of novel marine diterpenoid udoteatrial hydrate was synthesiz
ed from (+)-genipin as a chiral building block via homogeranyl lactone
obtained by an 1,4-addition of lithiated geranyl sulfone to the key i
ntermediate, exomethylene lactone. The stereochemistry of newly formed
stereogenic center at C5 was carefully examined by comparing H-1-NMR
spectra of each diastereomer of homogeranyl lactones with those of mod
el compounds, stereochemistries of which were confirmed by single crys
tal X-ray determination. The exomethylene lactone was successfully pre
pared from genipin through a catalytic hydrogenation Of C6-C-7 double
bond in cyclopentene ring in genipin. Our synthesis culminating the sy
nthesis of antipode of udoteatrial hydrate could confirm the absolute
configuration of udoteatrial hydrate as (2aS, 4aS, 5S, 7bR). The analo
gues of antipode of udoteatrial hydrate were also synthesized from exo
methylene lactone. Those analogues were subjected to the cytotoxic ass
ay to find that diacetates of analogues involving homogeranyl side cha
in were cytotoxic against human carcinoma KB and A-549 cells in vitro.