Isolation from the Mediterranean Stoloniferan Coral Sarcodictyon roseum of Sarcodictyin C, D, E, and F, Novel Diterpenoidic Alcohols Esterified by (E)- or (Z)-N(1)-Methylurocanic Acid. Failure of the Carbon-Skeleton Type as a Classification Criterion

Article abstract of DOI:10.1002/hlca.19880710504

It is shown here that the stoloniferan coral Sarcodictyon roseum of east Pyrenean waters contains four novel diterpenoids, sarcodictyin C ((-)-3), D ((-)-4), E ((+)-5), and F ((+)-6), which are related to sarcodictyin A (=(-)-(4R,4aR,7R,10S,11S,12aR,1Z,5E,8Z)-7,10-epoxy-3,4,4a,7,10,11,12,12a-octahydro-7-hydroxy-6-(methoxycarbonyl)-1,10-dimethyl-4-(1-methylethyl)-benzocyclodecen-11-yl (E)-N'-methylurocanate; (-)-1), previously isolated from the same coral.Sarcodictyin C ((-)-3) and D ((-)-4) are the 3α-hydroxy and 3α-acetoxy derivatives of (1)-1, sarcodictyin E ((+)-5) is the (Z)-urocanate isomer of (-)-3, and sarcodictyin F ((+)-6) is the 1α-hydroxy-2-ene isomer of (-)-3.In all cases, the nine-membered ring is locked, and the molecule stabilized, by the urocanic appendage; when this is removed in MeOH/KOH, the C(11)-O^- function is free to attack at C(5), and retro-condensations then lead to the ring-contracted butenolides 11 (from (-)-3) or 10 (from (-)-1) with extrusion of the hydroxyfuran nucleus (Scheme 3).Under the same conditions, with (-)-3, the C(3)-O^- group competitively attacks at C(5), the hydroxyfuran nucleus is expelled, and aldehyde 14 is formed.Peculiarly, in the reaction of (-)-3 with MeOD/KOD, the ring-contracted butenolide 17 contains D at the 4'-ax position.The sarcodictyins are unique in these chemical properties, not shared by the cladiellanes which have the same C-skeleton.