A formal asymmetric synthesis of pentalenolactone E (1b) phosphonate salt 17a ultimately led to the ketene dithioacetal 22. The angular intermediates 25a/b were obtained from and pentalenolactone F (1a) has been accomplished. Ozonolysis of the diphenyl-substituted triquinane 3 and Kauffmann 22 by reduction to give the linear hemiacetals 24a/b, which rearranged to the dithio ortholactones 25a/b in the presence methylenation of ketone 5 with WOCl 3 /2 MeLi yielded the unsubstituted triquinane 9. The crucial rearrangement of the of acid. Introduction of the double bond and deprotection were accomplished via selenation of 25a/b with N,N-diethyl-linear triquinanoid lactone 11 to the angular triquinanoid lactone 14a was accomplished using orthoformate and acid in benzeneselenylamide and treatment of selenides 30a/b with silver nitrate. The unsaturated aldehydes 28 and 29 thus ob-methanol. Subjecting triquinanes 14a/b to the selenoxide method gave triquinene 15. Homologation of γ-lactone 15 to tained were converted to 2 and 31, respectively, by oxidation with manganese dioxide in the presence of sodium cyanide, the angular diquinanoid δ-lactone 2 via a Horner-Wadsworth-Emmons or Peterson reaction of hemiacetals 16a/b methanol and acetic acid. Alkene 2 was isolated by crystallization. was, however, not successful. Chemoselective reduction of 14a afforded hemiacetals 21a/b, reaction of which with the