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‐l H ‐imidazol‐4‐yl)acrylic acid). They are sarcodictyin A ( = (−)‐(4 R ,4a, R , 7 R ,10 S ,11 S ,12a R ,l Z ,5 E ,8 Z )‐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‐l H ‐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 LiAlH 4 followed by benzoylation giving dibenzoate 7. Absolute configurations are based on Horeau's method of esterification of (+)‐ 4 .