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.