A Novel Atisane Diterpenoid fromSpiraea japonica var.acuta

A novel ent-atisane lactone, spiramilactone E (1), was isolated from Spiraea japonica var. acutaYU. Its structure was elucidated by extensive spectroscopic analyses, and unequivocally confirmed by single-crystal X-ray diffraction (Fig. 2). Compound 1 contains a gamma-lactone moiety between the 6-OH function and C(20), and beta-configuration for the 7-OH group, in contrast to known related diterpenes previously isolated from the S. japonica complex.