Sarcodictyin A and Sarcodictyin B, Novel Diterpenoidic Alcohols Esterified by (E)-N(1)-Methylurocanic Acid. Isolation from the Mediterranean Stolonifer Sarcodictyon roseum

The Mediterranean stolonifer Sarcodictyon roseum (= Rolandia rosea) (Cnidaria, Anthozoa, Alcyonaria, Stolonifera, Clavulariidae) is shown to contain two novel diterpenoidic alcohols esterified by (E)-N(1)-methyl-urocanic acid (= E)-3-(l-methyl-lH-imidazol-4-yl)acrylic acid). They are sarcodictyin A ( = (−)-(4R,4a,R, 7R,10S,11S,12aR,lZ,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)-3-(1-methyl-lH-imidazol-4-yl)acrylate; (−)-1) and sarco-dictyin B (the 6-(ethoxycarbonyl analogue; (−)-2). The assignment of the structures is mainly based on 1D- and 2D-NMR data, as well as on chemical transformations of (−)-1, such as transesterification with MeONa/MeOH giving methyl (E)-N(1)-methylurocanate (3) and the free alcohol (+)-4 and reduction with LiAlH4 followed by benzoylation giving dibenzoate 7. Absolute configurations are based on Horeau's method of esterification of (+)-4.