Neo-clerodane diterpenoids from Ajuga parviflora

neo-Clerodane diterpenoids from Ajuga: structural elucidation and biological activity

“…Ivain III (Camps et al 1982) and 15-ethoxydihydroajugapitin (Camps et al 1984b) were isolated as single enantiomers but no C-15 stereochemistry was assigned [15-ethoxydihydro ajugapitin was quoted as a C-15 epimeric mixture (Beauchamp et al 1996)]. The reported NMR data for H-11 (d 4.48 in both), provides the evidence for C-15 a configuration of the isolated isomer.…”

“…On a semisystematic bases, the structures of lupulin A, B and D (Chen et al 1996b) could be described as 15b-methoxydihydroajugapitin, 15a-methoxydihydrocaryoptinyl 2-methylbutanoate and 15a-methoxydihydroclerodin respectively. However, in the corresponding X-ray report for lupulin The compound (C-15a stereochemistry; single; erroneously quoted as an epimeric mixture (Beauchamp 1996)) was reported with no stereochemical assignment for C-15. a-Assignment based on the NMR data matching those of 15b-ethoxy-14-hydroajugapitin (Beauchamp 1996), prior to stereochemistry revision (cf.…”

“…However, in the corresponding X-ray report for lupulin The compound (C-15a stereochemistry; single; erroneously quoted as an epimeric mixture (Beauchamp 1996)) was reported with no stereochemical assignment for C-15. a-Assignment based on the NMR data matching those of 15b-ethoxy-14-hydroajugapitin (Beauchamp 1996), prior to stereochemistry revision (cf. Ben Jannet 1999) d Described as a subspecies (http-2) e Structural reassignment proposed (Coll 2002) f This paper provides for isolated diterpenes the corresponding original reference only for ajugamarin-A2 g The formula shows a neo-clerodane skeleton, but the paper displays an ent-neo-clerodane structure from the view with ellipsoids, with a 15a-methoxy in both h The formula shows a 15b-methoxy ent-neo-clerodane skeleton but from the view with ellipsoids a 15a-methoxy neoclerodane is displayed i The compound was previously described, but it was reported as new j One name appears in the abstract, the other in the experimental part k Structural assignment revised (Carbonell 2001) m Mixture of C-15 epimers (Chen et al 1996a), whereas the formula (with a few stereochemistries undisclosed) shows the corresponding neo-clerodane skeleton as expected and 15a-methoxy substitution (referred as C 17), the view with displacement ellipsoids depicts an ent-neo-clerodane structure and yet a 15a-methoxy substitution.…”

“…On the other hand, the structural assignments for clerodinins C and D were based on the ''old'' thermodynamic stability rational because there was no observed NOE between H-11 and the CH 2 of OEt (Beauchamp et al 1996), as well as for 3b-acetoxyclerodinin C and the 15-ethoxydihydroajugapitin analogues. The NMR data reported for 15a-assignments (d 3.99 and 3.98) point out the corresponding b orientation and vice versa, and thus, the structural assignments require again the corresponding reversal (clerodinin C and 3b-acetoxyclerodinin C change from b to a; clerodinin D change from a to b; and the 15-ethoxydihydroajugapitin analogues exchange assignment).…”

Cholinesterase‐Inhibiting Withanolides from Ajuga bracteosa

“…Further biological screening of the ethanolic extract and of the AcOEt-soluble fraction revealed significant inhibitory activity against cholinesterase enzymes, prompting us to carry out bioassay-guided isolation studies on AcOEt-soluble fraction of this plant. Herein, we report the isolation and structure elucidation of three new withanolides, bracteosins A ± C, 1 ± 3, and four known diterpenoids, dihydroclerodin-1 [5], clerodinin A [6], lupulin A [7], and dihydroajugapitin [8].…”