Studies on the Constituents of the Seeds of Hernandia ovigera L. VII. : Syntheses of (±)-Hernolactone and (±)-Hernandin

Two new lignans, hernolactone (1) and fernandin (2), isolated from the seeds of Hernandia ovigera L. were synthesized in recemic forms. Firstly, (±)-1 was obtained by utilizing the conjugate addition reaction of 4 with butenolide followed by alkylation with trimethoxybenzyl bromide and subsequent removal of the protecting groups. Synthesis of 2 was pursued using the corresponding 4-phenyl-1, 2-dihydronaphthalene lactone(18). The cleavage of the lactone moiety of 18 afforded an unsaturated hydroxy acid (22). Subsequent hydrogenation of 22 followed by acidification with concetrated hydrochloric acid gave isopicrobernanadin (21), leaving the 2, 3-trans, 3, 4-cis hydroxy acid (23), which was lactonized by means of N, N-dicyclohexylcarbodiimide to afford (±)-2.