“…A survey of the saturated 7-1actones in a variety of molecules reveals a common conformation in which the C,~-CO-O-C v group is planar and the fl-C atom is at the flap of this envelope conformation. This usual arrangement is found for example in 19-acetylteuspinin (Eguren, Fayos & Perales, 1981), nagilactone A diacetate (Hirotsu, Higuchi, Shimada, Hayashi & Sakan, 1975), (+)-or (+)-trans-lfl-carboxy-8fl-hydroxy-1 a,4a,6fl-trimethyl-5-oxodecahydronaphthalene lactone (Adinolfi, Benedetti, Di Blasio & Pedone, 1975a,b). In all these molecules the fl-C is displaced from the lactone ring plane by about 0.6 A.…”