Triterpenoid glycosides from Stauntonia chinensis
A new bidesmoside triterpenoid saponin, named stauntoside C1 (1), along with three known saponins (2–4) was isolated from Stauntonia chinensis DC. (Lardizabalaceae). Their structures were established by means of spectral and chemical methods as 3-O-β-d-xylopyranosyl-(1 → 2)-O-β-d-xylopyranosyl-(1 → 3)-O-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl oleanolic acid 28-O-α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester (1), scabiosaponin E (2), sieboldianoside B (3), and kizutasaponin K12 (4).
Triterpenoid saponins from Stauntonia chinensis
A new triterpenoid saponin, named stauntoside A (1) along with four known saponins (2,3,4,5) was isolated from Stauntonia chinensis DC., (Lardizabalaceae). Their structures were elucidated by spectroscopic analysis and chemical methods as 3-O-α-l-arabinopyranosyl-30-norhederagenin -28-O-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester (1), 3-O-α-l-arabinopyranosyl-30- norhederagenin-28-O-α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester (2), 3-O-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl-30-norhederagenin-28-O-α-l- rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester (3), 3-O-α-l- arabinopyranosyl-hederagenin-28-O-α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 6)-β-d- glucopyranosyl ester (4), 3-O-α-l-rhamnopyranosyl-(1 → 2)-α-l-arabinopyranosyl-hederagenin -28-O-α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 6)-β-d-glucopyranosyl ester (5). The 1H and 13C NMR data for Glycoside L-G1 or Sinofoside A are paradox in the reported before. Thus, the structure elucidation of saponin 2, known as Glycoside L-G1 or Sinofoside A, was discussed and the unambiguous assignments were given.
Highly enantio- and diastereoselective synthesis of β-methyl-γ-monofluoromethyl-substituted alcohols.
Enanatiopure β-methyl-γ-monofluoromethyl alcohols were prepared from the allylic alkylation between fluorobis(phenylsulfonyl)methane with Morita-Baylis-Hillman carbonates. The reaction was catalyzed by using the Cinchona alkaloid derivative, (DHQD)(2)AQN. The origin of the stereoselectivity was verified by DFT methods. Calculated geometries and relative energies of various transition states strongly support the observed stereoselectivity.