From: Hr. Dr. S. Shapiro (toukie$##$zui.unizh.ch)
Date: Fri Jun 25 1999 - 09:18:08 EDT
Dear Colleagues;
I am interested in obtaining a "pure" sample of a complex between
2-hydroxypropyl-beta-cyclodextrin and a very hydrophobic ligand. I have
tried to synthesize the complex in several ways, but so far my yields
(based on NMR analyses) range from 10-25%, the remaining percentage being
uncomplexed 2-hydroxypropyl-beta-cyclodextrin. The complex appears to have
a very low dissociation complex in water (i.e., the complex is quite stable
in aqueous milieux), and is totally soluble in water but unstable in
organic solvents such as methanol (NMR results). Thus, when the complex is
dissolved in methanol the ligand appears to rapidly and irreversibly exit
the cyclodextrin host molecule.
I would like to purify the cyclodextrin-ligand complex and separate it
away from the residual uncomplexed cyclodextrin present in the recovered
product. Moreover, this will have to be done in an aqueous environment to
preclude decomposition of the complex. I thought about the possibility of
gel permeation chromatography, but the difference in molecular weight
between the complex (1700) and uncomplexed cyclodextrin (1400) is not so
great. Does anyone know of a precedent for separating a cyclodextrin
complex from the uncomplexed cyclodextrin using gel permeation
chromatography? If so, I should be most grateful to receive literature
references which I may then go to the library and read. Any _other_
suggestions about separating the two substances in question are also
welcome, particularly if they are accompanied by references.
Thanks in advance to all responders,
S. Shapiro
toukie$##$zui.unizh.ch
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