Tatjana V. Rybalova

Stereochemistry of hydrogen peroxide-acetic acid oxidation of ursolic acid and related compounds

Abstract Stereochemistry of a number of oxidized derivatives of ursolic acid was established using NMR data and X-ray analysis. Full signal assignments were made in 1H and 13C NMR spectra of 26 natural and synthetic ursane type triterpenoids. Possible mechanisms of oxidation of ursolic acid and related compounds by peracids, as well as mechanisms of secondary processes, were formulated basing on chemical behavior and molecular mechanics calculations of the starting materials and certain intermediate species.

Study of chiral β-enaminones prepared from pyrrolidine, cytisine, salsoline and 2-amino-1-(4-nitrophenyl)propane-1,3-diol: resolution of salsoline via diastereomeric modified carane-type β-enaminones

Abstract A series of novel optically active β-enaminones have been prepared regio- and stereoselectively from primary and secondary amines (pyrrolidine, cytisine salsoline and 2-amino-1-(4-nitrophenyl)propane-1,3-diol) and (+)-3-carene-derived β-chlorovinylketone. Resolution of the isoquinoline alkaloid salsoline has been demonstrated as well as isolation of a single diastereomeric adduct from racemic 2-amino-1-(4-nitrophenyl)propane-1,3-diol.

Syntheses and crystal structure of bridged Os3-clusters with chiral 3-carane-type ligands

Abstract Reaction of (μ-H)2Os3(CO)10 cluster with (1S,3S,6R)-3-dimethylaminocarane-4-one E-oxime results in loss of dimethylamino group and formation of (μ-H)Os3(CO)10(μ-ONC) cluster (43%). Treatment of cluster Os3(CO)11(NCCH3) with (1S,3S,6R)-3-mercaptocaran-4-one E-oxime gives cluster (μ-H)Os3(CO)10(μ-S⋯) in 86%, whose structure was proved by X-ray single crystal analysis. Decarbonylation of the later compound with (CH3)3NO leads to a diastereomeric mixture of (μ-H)Os3(CO)9(μ,η2-(S,N)⋯) clusters in 64% yield.

Novel optically active pyrazole ligands derived from (+)-3-carene

Abstract Reactions of chiral β-diketone with racemic hydrazines as well as reaction of chiral pyrazole with cyclohexene epoxide and trans-stilbene epoxide have been examined as the routes to optically active pyrazolylethanols. Diastereomerically pure products have been isolated by crystallization or column chromatography in good yields.