Jr. Falck et al., TERPENOID CHIRONS - PREPARATION AND TRANSFORMATIONS OF Y-1,1,4A(R),6-TETRAMETHYL-TRANS-DELTA(5,6)-OCTALIN, Tetrahedron letters, 35(13), 1994, pp. 2013-2016
Octalins 4 and 5 are prepared conveniently in 3 steps from commercial
18beta-glycyrrhetinic acid and converted to a variety of functionalize
d trans-AB ring chirons.