a compound extracted from = bacteria gave good antibacterial activity.
However, the NMR chemical shifts correspond to two very similar = structures.

Can a calculation or modelling priortize one of the = 2 proposed structures significantly
to be the most stable and = reliable one to argue that it is the naturally occurring compound?

Attached are the proposed structures A and B. I suggest to do ab initio calculations at the MP2 level with good basis = set and compare their relative energies.

However, I am not sure = that this will be enough! Any other ideas will be very helpful? Thank you,

Did = you measure the NMR in solution or crystal phase?

The differences between the solution and solid st= ate results is probably at least as large as the difference between A &= B. Hence the calculation should reflect the experimental condition. If in = solution, then the proposed DFT approach will be ok. If in solid state, the= n you will first need to determine crystal structure and compute the NMR of= the crystal.

<= /o:p>

George Fitzgerald, Ph.D.

George.Fitzgerald..accelrys.com

+1 858 799 5360

<= p class=3DMsoNormal>From: owner-chemistry+gfitzgerald=3D=3Daccelrys.com..ccl.n= et [mailto:owner-chemistry+gfitzgerald=3D=3Daccelrys.com..ccl.net] On Beh= alf Of Computational Chemist computationalchemist ~ ymail.com
Sen= t: Tuesday, October 29, 2013 8:00 AM
To: George FitzgeraldSubject: CCL:G: NMR chemical shifts correspond to two very similar = structures. Can a calculation or modelling priortize one of the 2 proposed = structures ?

&nb= sp;

 a compound extracted from bacteria gave good antibacterial activity.

However, the  NMR chemical shifts correspond to two v=
ery similar structures. 

Can a calculation or modelling priortize on=
e of the 2 proposed structures significantly 
to be the most stable and =
reliable one to argue that it is the naturally occurring compound? 

=
Attached are the proposed structures A and B.

I sugg=
est to do ab initio calculations at the MP2 level  with good basis set=
 and compare their relative energies. 

However, I am not sure that t=
his will be enough!

Any other ideas will be very hel=
pful?

Thank you,

= --_000_55AC410F3302E740AC9EC50011F73E8F124A8D96AFEXCH1COLOacce_-- From owner-chemistry@ccl.net Wed Oct 30 15:57:00 2013 From: "Jerome Kieffer Jerome.Kieffer|*|terre-adelie.org" To: CCL Subject: CCL: NMR chemical shifts correspond to two very similar sructures Message-Id: <-49294-131030085522-8972-QFVkWDEHn2hdPvFzobcALA : server.ccl.net> X-Original-From: Jerome Kieffer Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII Date: Wed, 30 Oct 2013 13:55:05 +0100 Mime-Version: 1.0 Sent to CCL by: Jerome Kieffer [Jerome.Kieffer,terre-adelie.org] On Wed, 30 Oct 2013 09:18:17 +0100 "Rudolf Herrmann rudolf.herrmann ~~ physik.uni-augsburg.de" wrote: > I would suggest to calculate the 1H and 13C chemical shifts (GIAO > method with DFT - even 6-31G** is not bad for that purpose) for all > possible isomers, and compare _all_ shifts with the experimental data. 1H NMR requires a very good description of the solvent environment which is usually not the case. I would advice to focus on 13C NMR. There are basis-sets optimized for nuclear spectroscopies, focusing on the description of the electronic cloud near the nucleus. You should use one of them for the single point GIAO. Cheers, -- Jerome Kieffer From owner-chemistry@ccl.net Wed Oct 30 16:50:00 2013 From: "David A Mannock dmannock{=}ualberta.ca" To: CCL Subject: CCL: Proceedings of Dick Cramer's award symposium freely available Message-Id: <-49295-131030162726-28152-QTSK6M3f/1F8NgNs+FMNPg*_*server.ccl.net> X-Original-From: David A Mannock Content-Type: multipart/alternative; boundary=047d7b5da0dbd2615304e9fb2881 Date: Wed, 30 Oct 2013 14:27:17 -0600 MIME-Version: 1.0 Sent to CCL by: David A Mannock [dmannock+*+ualberta.ca] --047d7b5da0dbd2615304e9fb2881 Content-Type: text/plain; charset=ISO-8859-1 Wendy, this is a very useful summary of the area. Will it appear in print as a citable document? Thanks, David On Tue, Oct 29, 2013 at 9:50 PM, Wendy A Warr wendy~~warr.com < owner-chemistry-$-ccl.net> wrote: > > Sent to CCL by: "Wendy A Warr" [wendy{:}warr.com] > I have written a 20-page article with 84 references describing the > symposium honoring Richard (Dick) Cramer, winner of the ACS CINF Herman > Skolnik Award. It is freely available at > http://bulletin.acscinf.org/node/536. > > Dr. Wendy A. Warr > Wendy Warr & Associates > 6 Berwick Court, Holmes Chapel > Cheshire, CW4 7HZ, England > Tel./Fax +44 (0)1477 533837 > wendy[A]warr.com > http://www.warr.com > Skype: wendyannewarr > Twitter: [A]WendyAnneWarr> > > --047d7b5da0dbd2615304e9fb2881 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

Wendy, this is a very useful summary of the area. Will it = appear in print as a citable document? Thanks, David

On Tue, Oct 29, 2013 at 9:= 50 PM, Wendy A Warr wendy~~warr.com <owner-chemistry-$-ccl.net> wrote:

Sent to CCL by: "Wendy A Warr" [wendy{:}warr.com]
I have written a 20-page article with 84 references describing the symposiu= m honoring Richard (Dick) Cramer, winner of the ACS CINF Herman Skolnik Awa= rd. It is freely available at http://bulletin.acscinf.org/node/536.

Dr. Wendy A. Warr
Wendy Warr & Associates
6 Berwick Court, Holmes Chapel
Cheshire, CW4 7HZ, England
Tel./Fax +44 (0)1477 533837
wendy[A]warr.com
http://www.warr.com Skype: wendyannewarr
Twitter: [A]WendyAnneWarr

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