| Popis: |
On the influence of phenylboronic and diphenylborinic acid on the paper chromatographic mobilities of cardenolides and bufadienolides Phenylboronic acid and diphenylborinic acid were studied as to their influence on the paper chromatographic mobilities of cardenolides and bufadienolides with and without a cis -1,2- or cis -1,3-diol group. At low concentrations, phenylboronic acid and at higher concentrations, diphenylborinic acid increases the mobility of nearly all investigated cis -1,3-diols with a tertiary OH-group. At higher concentrations both acids enhance the mobilities of most of the cis -1,3- and cis -1,2-diols without a tertiary OH-group, too. It is concluded that there are two basic prerequisites for the derivatization of cis -1,2- or cis -1,3-diols: (1) the capabilities of the diol to reach an O-O distance like that in phenylboronic acid esters or in diphenylborinic acid complexes; (2) the absence of a considerable steric hindrance by a substituent near the reactive diol group. Among the four studied rhamnosides being 1,2-diols two do not react from hitherto unknown reasons. |
