Dear Jaekuy,
if you suspect your compounds to have different physical
properties, it means that they can't be enantiomeric products. They can
only
be diastereoisomers or configurational isomers, which may not allow to
differentiate between them by HPLC since for example, if you have two
diastereoisomers that differ by only one center, you may not see a
difference
on a chromatogram (depending on your system ). However, as far as I
remember,
non enantiomeric products are distinguishable by NMR (even when using
achiral
solvent) since the environment of an atom in one diastereoisomer will be
different than the environment of the same atom or group of atom in
another
environement which will affect its chemical shift. Coming back to the
basic,
if you have different compounds, you may which to get informations such
as
melting point, density, refractive index or any other physical property of
the
compounds you are dealing with. UV and especially IR could prove
useful in
determining if you have different compounds, given they are quite pure.
Don't
forget that the color change may only be coming from impurity in you
compounds. Have you also though about possible oxidation?
Jean Martin, Montreal, Quebec, Canada
jean_alchemist@msn.com
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From: PharmTech
Sent: 11 juin, 1997 14:15
To: pharmtech@pharmweb1.man.ac.uk
Dear everybody
My work is to screen the compounds in order to search a drug candidate,
so I
always have to handle with new chemical compounds. I have been doing
this
since last year.
Whenever they give me a new chemical compound for a screening, they
bring an
analysis sheet which contains NMR data and HPLC data of the
compound. When
they give me the same compound with a new lot number, they also bring
a new
analysis sheet which makes me sure that this compound is identical to
those
given to me previously. But, I think the physical properties of the
compound
are a little different among the compounds, despite the analysis sheet
which
shows the same peak patterns and the same retention times etc to those
of
the compounds which were either synthesized or isolated previously. For
example, the color of dissolved compound in the same solvent is not
identical to those that were given to me previously. I think it is
important, because this different physical properties of the same
compound
have different effects on the same experiment, which makes the
experiment
less reproducible.
I want to know if there are useful tests to confirm that the physical
properties of the compound are identical to those of the compound made
previously.
Thank you.
Jaekyu Shin
e-mail address : nogury@cheiljedang.com
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