A Macrocyclic Dimeric Diterpene with aC₂Symmetry Axis

Abstract

An unprecedented macrocyclic dimeric diterpene containing a C2 symmetry axis was isolated from Acacia schaffneri . This compound, named schaffnerine, was characterized as (5S,7S,8R,9R,10S,17S,5'S,7'S,8'R,9'R,10'S,17'S)-7,8:7,17':16,17:17,7':7',8':16',17'-hexaepoxy-7,8-seco-7',8'-seco-dicassa-13,13'-diene (1) from its spectroscopic data. Comparison of its experimental vibrational circular dichroism spectrum with that calculated using density functional theory, at the B3LYP/DGDZVP level, assigned its preferred conformation and absolute configuration. The latter was confirmed by evaluation of the Flack and Hooft parameters obtained after single-crystal X-ray diffraction analysis.

Recent advances in the use of vibrational chiroptical spectroscopic methods for stereochemical characterization of natural products

“…141 Several dimeric stilbene glucosides were isolated from Gnetum africanum and had their absolute congurations assigned using VCD and DFT [B3PW91/6-31G(d,p)] calculations. Finally, the bioactive compound (+)-schizandrin (116), isolated from Schisandra sphenanthera, had its absolute conguration reassigned using VCD and DFT [B3LYP/6-311+G(d)] calculations for two the diastereomers possible. Compounds (À)-gnemonoside C (113) and (À)-gnemonoside D (114) were assigned as 7aS,8aS.…”

“…5S,8S,9S,10R,14R)-66 using VCD and DFT (B3LYP/ DGDZVP) calculations 115. Preferred conformations and the absolute conguration of the unprecedented macrocyclic dimeric diterpene (À)-schaffnerine (67), isolated from Acacia schaffneri, were determined using VCD and DFT (B3LYP/ DGDZVP) calculations 116. This molecule was assigned as 5S,7S,8R,9R,10S,17S,5 0 S,7 0 S,8 0 R,9 0 R,10 0 S,17 0 S. The absolute conguration of the rare isoneoamphilectane carbon skeleton, present in marine diterpenes isolated from the sponge Svenzea ava, was determined using VCD and DFT [B3LYP/6-31G(d)] calculations 117.…”

Progress in the Chemistry of Organic Natural Products 100

“…Such studies were performed on crambin (255), myoglobin (256), lysozyme (257), human transthyretin (258), gamma-chymotrypsin (259), type-III antifreeze protein (260), the trypsin-BPTI complex (261), hemoglobin (262)(263)(264)(265), carbonic anhydrase II (266), insulin (267), ribonuclease A (268), elastase (269), HIV protease (270,271), diisopropyl fluorophosphatase (272), photoactive yellow protein (PYP) (273), dihydrofolate reductase (274), d-xylose isomerase (275), human aldose reductase (276), concanavalin A (277,278), rubredoxin (279), and endothiapepsin (280). Preliminary reports describing the collection of neutron diffraction data concern endoxylanase II from Trichoderma longibrachiatum (281), human ABO(H) blood group A glycosyltransferase (282), porcine pancreatic elastase (270),…”

“…The capability of Nature to biosynthesize unexpected molecules with a high degree of symmetry is exemplided from a further study of the aerial parts of the legume tree Acacia schaffneri (270). The study allowed the isolation and structural elucidation of schaffnerine (181) a macrocyclic dimeric diterpene with a C 2 symmetry axis.…”

Antiproliferative Activity of seco-Oxacassanes from Acacia schaffneri

“…In this work, the cytotoxic activity of the hexane, chloroform, and methanol extracts from the aerial parts of Acacia schaffeneri (S. Watson) F. J. Hermann (Leguminosae), as well as of the diterpenetype seco-oxacassanes 1-3 ( Figure 1) identified in this species [11,12], was explored by the sulforhodamine B (SRB) test. Furthermore, a preliminary study of the mechanism of the cytotoxic activity exhibited by diterpene 2, through cell cycle analysis, DNA repair pathways, and inhibition of migration capacity was carried out.…”