New neoclerodane diterpenoid containing an oxetane ring isolated from Teucrium chamaedrys. X-ray structure determination

Abstract

Continuing our studies on diterpenic compounds from the Teucrium species (family Labiatae),2"5 we now report the isolation and structure determination of a new compound from T. chamaedrys L., a species in which several new neoclerodane diterpenoids have been previously found.6-12 The structre of this new diterpenoid, chamaedroxide, has been shown to be 40, 6|3:15,16-diepoxy-2d-hydroxyneocleroda-13( 16),14-diene-18,19:20,12(S)diolide (l),13 and it was established as follows.Combustion analysis and mass spectrometry indicated the molecular formula 02 2207 for chamaedroxide (1). Its

Complete assignments of the 1H and 13C NMR spectra of six highly functionalized neoclerodane diterpenoids

“…The NOESY spectra of 4-6 provided sure criteria for distinguishing both protons of the C-19 methylene group in all these substances and those of the C-11 methylene of 6, as summarized in Tables 3 and 4 Table 4 complete the partial data published previously 9,12 on these compounds and, in the case of 6, the coupling constant values (Table 4) and the NOESY spectrum (Table 3) were in agreement with the boat conformation of both A and B rings of chamaedroxide (6,3,10 B and 7,10 B conformations, respectively, symmetrically disposed at both sides of the C-5-C-10 bond), that was established by an x-ray diffraction analysis. 12 On the other hand, the 13 C NMR assignments for 4 ( Table 2) are identical with those reported in the literature, 9 whereas the 13 C NMR spectra of 5 and 6 (Table 2) have not been published previously.…”

“…7,9,12 a All these assignments were in agreement with HSQC, HMBC and NOESY spectra. b In this compound, the decalin part possesses a boat conformation for both A and B rings ( 3,10 B and 7,10 B, respectively) and consequently, the H-1˛, H-2˛, H-3ˇ, H-6˛, H-7ˇand H-10ˇprotons are axially oriented, whereas the H-1ˇ, H-3˛, H-7˛and H-8ˇhydrogens are equatorial substituents.…”

“…Br., whereas chamaedroxide (6) was found 12 in the acetone extract of Teucrium chamaedrys L. The structures of 1-6 were established by chemical transformations and IR, UV and 1 H and 13 C NMR spectroscopic studies 7 -10,12 and, in the case of 2 and 6, by single-crystal x-ray diffraction analyses. 8,12 Complete 1 H NMR assignments of 1-6 have not been performed previously, 7,9,10,12 particularly those corresponding to the pro-R and pro-S hydrogens of the C-19 (in 1-6) and C-11 (in 1-3 and 6) methylene groups, and those of the C-3 0 methylene of the pyrazoline part of 3. The previous assignments 7,9 of the 13 C NMR spectra for 1, 2 and been recorded previously.…”

“…The previous assignments 7,9 of the 13 C NMR spectra for 1, 2 and been recorded previously. 7,9,12 These facts, together with the biological interest of the neoclerodane diterpenoids, suggested attempting the complete assignment of the 1 H and 13 C NMR spectral data of 1-6 in the hope they could be useful for future assignments of related compounds.…”

Diterpenoids

“…Salviacoccin (30) was obtained28a from Salvia coccinea whilst a combination of spectral and X-ray-crystallographic studies was used28b to assign the structure (31) to salvinorin, which is a constituent of S. divinorum. Some relatives of salviacoccin, (32) and (33), were obtained29 from Conyza podocephala (Compositae). Medicinal herbs of the genus Teucrium (Labiatae) are another well-documented source of clerodane diterpenoids.…”