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C36.50H46BrN5O5.50, orthorhombic, P212121 (no. 19), a = 9.771(3) Å, b = 19.853(2) Å, c = 20.763(3) Å, V = 4027.7 Å3, Z = 4, Rgt(F) = 0.046, wRref(F) = 0.056, T = 293 K.

The flavonolignan silybin (1), isolated from the seeds of milk thistle (Silybum marianum), occurs in nature as an equimolar mixture of two diastereoisomers, silybin A and silybin B, that exhibit different biologi- cal activities. The preparative production of optically pure silybin A and B in a diastereoisomeric purity greater than 95% was accomplished using immobilized Candida antarctica lipase B (Novozym 435) in a combination of two reactions: regioselective acetylation of a natural silybin mixture (1) and subsequent stereoselective alcoholysis of the resulting 23-O-acetylsilybin (2). Several grams of the optically pure sub- stances can be produced within one week using this new, robust and scalable process, which is selective, mild and high-yielding.

C18H24N2O3, orthorhombic, P212121 (no. 19), a = 9.868(1) Å, b = 10.877(1) Å, c = 15.458(2) Å, V = 1659.1 Å3, Z = 4, Rgt(F) = 0.065, wRgt(F) = 0.079, T = 293 K.

New method of separation of dansyl amino acid (Dns-AA) enantiomers by capillary electrophoresis (CE) using terguride based chiral selectors (CSs) was developed using linear polyacrylamide coated capillaries. Due to high UV absorption of all studied CSs only capillary was filled with CS, while inlet and outlet vials contained buffer solution only. Conditions for baseline separation of all Dns-AA under study have been found. L-Dns-AAs were eluted prior to D-Dns-AAs on all studied CSs. Use of optical antipode of allyl-terguride resulted in reversal of elution order of all Dns-AAs (D-form was eluted prior to L-form). The best enantioselectivity was achieved for hydroxyl group-containing AAs, i.e. serine and threonine. This finding is in good agreement with proposed mechanism of chiral recognition of these AAs determined by X-ray studies. Seven CSs with different N(1)-side chain unit, five of them designed for the preparation of silica based HPLC chiral stationary phases, were tested for their capability to resolve enantiomers of Dns-AAs. Different polarity and hydrophobicity of N(1)-side chains of the CSs resulted in different CS mobilities thus influencing the effective separation time in capillary. 1-(5-aminopentyl)-terguride showed the best enantioseparation and resolution for Dns-AAs studied.