Chlorofluoroacetic Acid as a Highly Versatile Derivatizing Agent: Assignment of Stereochemistry to Esters of Chiral Alcohols

(R)-2-{2-[(S)-(2'-Benzo-yloxy-1,1'-binaphthyl-2-yl)oxycarbonyl-amino]-3-phenylpropanamido-meth-yl}pyridinium picrate acetone solvate

In the crystal structure of the title compound, C(43)H(34)N(3)O(5) (+)·C(6)H(2)N(3)O(7) (-)·C(3)H(6)O, the large dimension and shape of the cation are responsible for the elongation of the ortho-rhom-bic unit cell. The ions and acetone mol-ecules are linked together by a system of hydrogen bonds involving an inter-molecular hydrogen bond between one N atom of the cation and the O atom of acetone and two inter-molecular hydrogen bonds between the cation N atoms and the O atoms of the picrate anion. No intra-molecular hydrogen bonds exist in the structure. The dihedral angle between the two naphthalene ring systems is 76.16 (13)°. The chiral C atom has a known R configuration, but this cannot be confirmed from this X-ray analysis.

Chiral derivatives of 2-(1-naphthyl)-2-phenylacetic acid

The spectral properties of diastereomeric esters and amides (1b-20b), derived from optically pure 2-(1-naphthyl)-2-phenylacetic acids (1-NPA), were systematically investigated. It was found that all compounds prepared exhibit the NMR spectral nonequivalence (Deltadelta) with regular sign distribution of particular groups according to the predicted model. Further, the analysis of data revealed that the phenyl ring is responsible for a shielding effect (upfield shift) instead of a naphthyl one. This conclusion is supported by the crystallographic analysis showing the almost ap-arrangement of the acid methine hydrogen atom and carbonyl group. In this arrangement, the phenyl ring faces toward the ester part of the molecule while the naphthyl one is orthogonal to the phenyl plane. Therefore, the mutual position of phenyl and alkyl groups with respect to the central molecule co-planarity thus determines the chemical shifts of the alcohol/amine substituents. The relative magnitude of the Deltadelta corresponds to those of Mosher's derivatives.

Resolution of chiral drugs by liquid chromatography based upon diastereomer formation with chiral derivatization reagents

Chiral derivatization reagents for resolution of biologically important compounds, such as chiral drugs by high-performance liquid chromatography (HPLC), based upon pre-column derivatization and diastereomer formation, are reviewed. The derivatization reagents for various functional groups, i.e., amine, carboxyl, carbonyl, hydroxyl and thiol, are evaluated in terms of reactivity, stability, wavelength, handling, versatility, sensitivity, and selectivity. The applicability of the reagents to the analyses of drugs and bioactive compounds are included in the text.

Cyclic chiral silyl derivatives for the determination of the absolute configuration of aliphatic diols by gas chromatography

[reaction: see text] Chiral bidentate silyl reagents have been developed for the GC analysis of aliphatic 1,3- and 1,4-diols. These reagents react with the diols to cyclic siloxanes, which allow the determination of their enantiomeric composition even in complex mixtures. The absolute configuration of 4,6-nonadecanediol 7, occurring in the lipids of sunflower pollen, has been determined to be (4S,6R) by comparison with derivatized synthetic enantiomers.