In the previous paper 1) we reported the structure of pentalenolactone G, a shunt pathway product of pentalenolactone biosynthesis, As a result of further screening for biosynthetic intermediates, we have isolated the less oxidized metabolites named pentalenic acid and pentalenolactone H from the fermentation broth of Streptomyces sp. From the acidic fraction containing pentalenolactone G 1) , was isolated pentalenic acid as its methyl ester (I) by preparative tic (benzene/ethyl acetate = 3:1, Rf 0,481:) LE, ClsHz+Os CM+m/e found 264.1705, calcd. 264.17251, oil, v=' 3450 cm-l(CH), 1710 and 163C(a,Srunsaturated ester) hMeoH )max 227 nm (E 5400) gave upon treatment with acetic anhydride/ pyridine a monoacetate, ClaHzsO4 (M+ m/e 306, M+-CHzCOzH found 246.1609, calcd. 246.16201, m.p. 6717~o~, 6H 1.67 (CHsCOz-) and 4.63 (a, J=5,0 Hz, CH&OzC&). 'H-and 13C-nmr spectral data3)of 2 and comparison with those of a dihydro derivative (III)of pentalenolactone G (yide infra) revealed the partial structure from Cl to Ce shown in Fig.1. ----. (The values show 6H and those in parentheses are coupling constants in Hz). r3C-('H} Long range selective proton decoupling (LSPB), a technique extensively exploited in the structural elucidation of pentalenolactone G (II) , proved the relationship between gem-dimethyl and Cl. Thus , eliminated long range coupling c3JcrH) from methyl resonances