Abstract By cleavage of the aromatic ring of 6,7-dihydroxy-tetraline (1) with peracetic acid 1,2-bis-carboxymethylene- cyclohexane (3 a) is obtained. The addition of one mole of water to 3 a leads to 1-hydroxy-1-carboxymethyl-2-carboxymethylene-cyclohexane (4), which is readily converted to the lactone 1-hydroxy-2-carboxymethylene-cyclohexane-γ-lactone-aceticacid-(1) (5). By melting of compound 4 or 5 1,2-dihydroxy-cyclohexane-diaceticacid-1 (1,2) -di-γ-lactone (6) is obtained. 1,2-bis-carboxymethylene-cyclohexane (3 a) shows a molecular asymmetry which is of a type similar as found in atropisomeric compounds. On the basis of conformational considerations it is demonstrated that in the dilactone 6 the cyclohexane ring is stabilized in the boat form. Cleavage of the aromatic A-ring of 2-hydroxy-estradiol- (17β) -acetate (7) with peracetic acid occurs in a manner analogous to that of compound 1, giving rise to 2,3-seco-Δ10(1)-estrenediol- (5ξ, 17β)-diacid-(2,3)-lactone-(2 → 5) -17-acetate (8 a). 8 a is converted to the methylester 9 and further to the corresponding estrone derivative 11 a. Estrone-[16-14C] was incubated with the 15 000 × g supernatant from rat liver homogenate in order to investigate the possibility if scission of the aromatic ring A of estrogens is a step in their katabolism. Substance 11 a was used as a carrier in these studies