Chromatographic behaviour of diastereoisomers

Additivity of retention of diastereoisomeric and enantiomeric arylphthalides, aryl(arylene)phthalides and aryldiphthalides of dyadic and triadic composition

For the first time, four series of new phthalide-containing heteroaromatic compounds were separated by reverse phase HPLC: OYO, OYS, SYS; OYOYO, OYOYS, SYOYS; SYSYS, SYSYO, OYSYO; OYYO, OYYS, SYYS, (where O - diphenyloxide, S - diphenylsulfide, Y - phthalide group). A fundamental difference was established in the chromatographic behavior of diaryl(arylene)diphthalides, built on the principle of "head-to-tail", and diaryldiphthalides with a structure of "head-to-head". The meso and chiral diastereoisomers of the former were eluted by one peak, while the latter existed in solution in the forms of stable cis (racemic form) and trans (meso form) rotamers with different retention times. It was shown that to calculate the retention times of related diarylphthalides, diaryl(arylene)phthalides, diastereoisomeric and enantiomeric diaryldiphthalides of an asymmetric structure, the half-sum rule can be applied according to which: tR(A-X-B)≈[(tR(A-X-A)+tR(B-X-B)]/2. For diaryl(arylene)diphthalides of a triadic structure, a modified additive scheme for calculating retention times is proposed, including multiplication and division operations: tR(A-A-A) = tR(A-A-B) × tR(A-B-B)/tR(B-B-B).

Solvent selectivity in the resolution of some regioisomeric and diastereomeric prostaglandin intermediates on silica

The possibilities of predicting the selectivity in the resolution of regioisomeric and diastereomeric prostaglandin intermediates on silica gel was investigated. A satisfactory correlation between log alpha and the solvent localization parameters m and m0 was obtained, confirming the importance of solvent-solute localization in determining alpha values. The results will be useful in developing further the theory of the selectivity of resolution.