Re: ORGLIST: Cahn-Ingold-Prelog Tests?

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From: Jonathan Brecher (jsb2$##$
Date: Tue Jul 03 2001 - 12:31:50 EDT

At 12:19 PM -0400 7/2/01, Rzepa, Henry wrote:
>Does anyone know of any collection of 3D molecule coordinates
>for molecules with explicit R or S assignment in the CIP conventions?
>As with most conventions, several programs claim to implement them,
>but its almost certainly a 90:10, 99:1 or other partial implementation.
>There are of course many "difficult" cases, and some which are
>impossible to assign within the accepted convention.
>We need to test the reliability of some of these programs against
>"valid" examples.

FYI, the implementation in ChemDraw 6.0.2 is -- to the best of our
knowledge -- 100% accurate. There are a few things that we don't pretend
to handle (planar chirality comes to mind), but in those cases we simply
won't offer a descriptor. When we do offer a descriptor, it's correct.

The implementation in ACD's products is also pretty good, and I think I
heard that they're going to be tweaking their last few problem areas in
their upcoming release. It's not a big deal either way -- you have to have
a really really really good understanding of the CIP rules just to come up
with the problem cases in the first place.

Jonathan Brecher
CambridgeSoft Corporation

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