The genus Otostegia (Lamiaceae) encompasses 33 species growing worldwide [1]. The Iran flora, comprises three species of this genus, which are growing in tropical
and subtropical regions. In traditional medicine, Otostegia persica is used for the treatment of malaria, headache, diabetes, stomachache, and rheumatoid
arthritis, but also to promote wound healing [2],[3]. Phytochemical investigations of a petroleum ether subfraction of O. persica extract resulted in isolation of three new labdane diterpenes with spiro skeleton
(1-3) and two derivatives comprising a furan ring (4 and 5). The relative configuration of the isolated compounds was established by analysis
of NOESY correlations along with 1H and 13C NMR and DP4+ probability calculations, while the absolute configuration was determined
by quantum chemical calculation methods and comparison of calculated and experimentally
obtained ECD spectra.
Therefore, the isolated compounds were identified as (2ʹ’S,3R,4a’’S,5R,5ʹR,6ʹ’R,8a’’S)-6ʹ’-hydroxy-5-methoxy-2ʹ’,5ʹ’,5ʹ’,8a’’-tetramethyldecahydro-2H,2ʹ’H-dispiro[furan-3,2ʹ-furan-5ʹ,1ʹ’-naphthalen]-3ʹ’(4ʹ’H)-one
(1), (2ʹ’S,3R,4ʹ’S,4a’’S,5R,5ʹR,6ʹ’R,8a’’S)-4ʹ’,6ʹ’-dihydroxy-5-methoxy-2ʹ’,5ʹ’,5ʹ’,8a’’-tramethyldecahydro -2H,2ʹ’H-dispiro[furan-3,2ʹ-furan-5ʹ,1ʹ’-naphthalen]-3ʹ’(4ʹ’H)-one
(2), (2ʹ’S,3S,4a’’S,5R,5ʹR,6ʹ’R, 8a’’S)-6ʹ’-hydroxy-5-methoxy-2ʹ’,5ʹ’,5ʹ’,8a’’-tetramethyldecahydro-2H,2ʹ’H-dispiro[furan-3,2ʹ
furan-5ʹ,1ʹ’-naphthalene]-2,3ʹ’(4ʹ’H)-dione (3), (4aS,7R,8aR)-4-(2-(furan-3-yl)ethyl)-7-hydroxy-3,4a,8,8-tetramethyl-4a,5,6,7,8,8a-hexahydronaphthalen-2(1H)-one
(4), (1S,4aS,7R,8aR)-4-(2-(furan-3-yl)ethyl)-1,7-dihydroxy-3,4a,8,8-tetramethyl-4a,5,6,7,8,8a-hexahydronaphthalen-2(1H)-one
(5).
