Diterpenes from teucrium capitatum L. X-ray crystal and molecular structure of capitatin

Chemical Transformations of the Neoclerodane Diterpenes Eriocephalin and Capitatin: An Access to 4,5-seco-Neoclerod-5(19)-ene Derivatives

“…Capitatin (6) : mp 167−168 °C (EtOAc/petroleum ether) (lit . 165−166 °C); [α] 21 D +137.2° ( c 0.352, CHCl 3 ); IR, 1 H NMR, 13 C NMR, and MS were identical to those previously reported 16 for capitatin; comparison (mmp, TLC) with an authentic sample confirmed the identity.…”

“…Oxidation of 2 with Jones' reagent gave capitatin (6, 49% yield, a neoclerodane diterpene previously isolated from Teucrium capitatum 16 ) and the keto aldehyde 7 (11%). The structure of 7 was confirmed by its spectroscopic data (see Tables 1 and 2, and Experimental Section) and those of other related neoclerodane derivatives.…”

“…Oxidation of 2 with Jones' reagent gave capitatin ( 6 , 49% yield, a neoclerodane diterpene previously isolated from Teucrium capitatum ) and the keto aldehyde 7 (11%). The structure of 7 was confirmed by its spectroscopic data (see Tables and , and Experimental Section) and those of other related neoclerodane derivatives. − The formation of compounds 6 and 7 from 2 can be rationalized by an initial acid catalyzed hydrolysis of the 20- O -acetyl group 9,15 and the subsequent oxidation of both closed and opened forms of the 20,12-hemiacetal.…”

“…This may be attributed to the instability of the starting material ( 8 ). The 1 H-NMR spectrum of 12 revealed that the reduction of the C-6 ketone occurred from the less hindered β-face (δ H-6 β 3.65 dd, J 6 β ,7 β = 3.9 Hz, J 6 β ,19A = 1.3 Hz). ,,,, …”

“…The 1 H-NMR spectrum of 12 revealed that the reduction of the C-6 ketone occurred from the less hindered β-face (δ H-6β 3.65 dd, J 6β,7β ) 3.9 Hz, J 6β,19A ) 1.3 Hz). 6,11,15,16,19 When compound 12 was treated with HCl under identical experimental conditions as those for 2 and 6, only compounds 13 (65%) and 14 (14%) were isolated; thus, indicating that route A of Scheme 1 is probably the mechanism for the transformation of 19-acetoxy-18-chloro-4R-hydroxy-6-oxo-neoclerodanes to their corresponding 18-chloro-4,6-dioxo-4,5-seco-neoclerod-5( 19)ene derivatives.…”