Cleavage of enantiomers of methano-1H-cyclooct[b]indol-9-ol and their absolute configuration

Chiral [6R and 6S-(6, 9, 10)]methano-1H-cyclooct[b]indol-9-ols were segregated into enantiomers through diastereomeric esters with (R)--trifluoromethylphenylacetic acid. The absolute configuration of the enantiomers was established by the NMR method using the shift reagent Eu(fod)₃ and the circular dichroism spectra.     

First total synthesis and reassignment of absolute configuration of diosniponol A and B

Enantioselective first total synthesis of diosniponol A and B has been achieved starting from commercially available vanillin. Wittig reaction, Keck allylation, and Prins cyclization reactions are the key steps involved in the target synthesis.     

Structure and absolute configuration of collutine

Summary A new base with the composition C₂₁H₂₅O₅N, mp 192–194°C, []_D -182°C, which has been called collutine, has been isolated from the epigeal parts ofColchicum luteum Baker.On the basis of UV, IR, NMR, and mass spectra and chemical reactions, the structure of 4-hydroxy-2,3, 6-trimethoxyhomomorphinandienone has been proposed for collutine.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 758–761, November–December, 1975.     

Vibrational circular dichroism study for natural bioactive schizandrin and reassignment of its absolute configuration

Bioactive natural product (+)-schizandrin was assigned as (7S,8S) using NMR. Recently, we obtained (+)-schizandrin from TCM Schisandra sphenanthera Rehd. et Wils. Its planar structure was well established using NMR and HR-MS including the reported references. Its absolute configuration is assigned using vibrational circular dichroism (VCD). By careful VCD investigation of (7S,8S) and (7S,8R) using B3LYP/6-311+G(d) methods, absolute configuration of (+)-schizandrin is assigned as (7S,8R). Electronic circular dichroism (ECD) was used for the discussion too and it gave the same conclusion.