No possible SMILES?

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No possible SMILES?

Noel O'Boyle
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Uncle Al claims no possible SMILES for his chiralanes:

http://www.coronene.com/blog/?p=1128#comment-8794

Perhaps a worthy challenge for our new stereocode....

- Noel

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Re: No possible SMILES?

Craig James-2
Noel O'Boyle wrote:
> Uncle Al claims no possible SMILES for his chiralanes:
>
> http://www.coronene.com/blog/?p=1128#comment-8794
>
> Perhaps a worthy challenge for our new stereocode....

I'm not sure what the challenge is.  The molecule plainly has a distinct mirror image.  Ignoring hydrogens, there are four symmetry classes before you even take stereochemistry into account.  If we number the symmetry classes 1 (starting in the center) through 4 (the farthest carbons from the center), then it's easy to see that for class 3, there are left- and right-handed connections.  That difference would propagate to class 2, and to class 1.

Why does Uncle Al say it "can't be stereolabeled even in principle"?  Am I overlooking something?

This is the same idea as a number of other situations we've seen, where the stereo labelings of one atom are only distinguished by the stereo labels of other atoms.  It's tricky, but not impossible.

(And who is "Uncle Al"? in real life?)

Craig


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Re: No possible SMILES?

Andrew Dalke
On Dec 2, 2009, at 8:04 PM, Craig A. James wrote:
> Noel O'Boyle wrote:
>> Uncle Al claims no possible SMILES for his chiralanes:
>>
>> http://www.coronene.com/blog/?p=1128#comment-8794

> I'm not sure what the challenge is.

I don't know the full chain which lead to that comment, but the source looks to have a posting on CCL, on the question of IUPAC naming:

Begin forwarded message:
> From: "Michel Petitjean petitjean.chiral : gmail.com" <[hidden email]>
> Date: November 20, 2009 8:26:23 PM GMT+01:00
> Subject: CCL: chemoinformatics / a nomenclature challenge

> Sent to CCL by: Michel Petitjean [petitjean.chiral%x%gmail.com]
> Dear CCLers,
>
> Here is my challenge: assign a name to the [6.6]chiralane, C27H28.
> The connection table is available from
> http://petitjeanmichel.free.fr/itoweb.petitjean.graphs.html#CHIR
> If somebody has a programme running successfully on this small molecule,
> please tell me and send me the name:
> until now, nomenclature assignment programmes failed !
> Furthermore, I would be delighted to know what name is
> generated from CAS or IUPAC rules.
> Many thanks.
>
> All my best,


As for who "Uncle Al" is, try chopping off the URL from that comment to get
 http://www.mazepath.com/uncleal/
Draw you own conclusions of the content of that page, then look at the meta tag and you'll see "Copyright 2009 Alan M. Schwartz".

No idea who that is.

                                Andrew
                                [hidden email]

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Re: No possible SMILES?

Noel O'Boyle
Administrator
In reply to this post by Craig James-2
2009/12/2 Craig A. James <[hidden email]>:

> Noel O'Boyle wrote:
>>
>> Uncle Al claims no possible SMILES for his chiralanes:
>>
>> http://www.coronene.com/blog/?p=1128#comment-8794
>>
>> Perhaps a worthy challenge for our new stereocode....
>
> I'm not sure what the challenge is.  The molecule plainly has a distinct
> mirror image.  Ignoring hydrogens, there are four symmetry classes before
> you even take stereochemistry into account.  If we number the symmetry
> classes 1 (starting in the center) through 4 (the farthest carbons from the
> center), then it's easy to see that for class 3, there are left- and
> right-handed connections.  That difference would propagate to class 2, and
> to class 1.
>
> Why does Uncle Al say it "can't be stereolabeled even in principle"?  Am I
> overlooking something?
>
> This is the same idea as a number of other situations we've seen, where the
> stereo labelings of one atom are only distinguished by the stereo labels of
> other atoms.  It's tricky, but not impossible.
>
> (And who is "Uncle Al"? in real life?)

The name is at the top of http://www.mazepath.com/uncleal/chiralan.htm

> Craig
>
>

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Re: No possible SMILES?

Andrew Dalke
In reply to this post by Andrew Dalke
On Dec 2, 2009, at 8:47 PM, Andrew Dalke wrote:
> I don't know the full chain which lead to that comment, but the source looks to have a posting on CCL, on the question of IUPAC naming:

Looking through the CCL thread, I got it wrong:

> Sent to CCL by: "Tobias Kind" [tkind]|[ucdavis.edu]
>
>
> Hello Michel,
> actually the name was already posted back in 2006 and 2009.
> 1) sci.tech-archive.net/Archive/sci.chem/2006-06/msg00154.html
> 2) darkhammer.multiply.com/journal/item/223

   ...
> http://petitjeanmichel.free.fr/itoweb.petitjean.graphs.html#CHIR
> If I wouldn't know better I would say that looks like a typical Uncle Al
> question, well it was :-)


Searching for '"Uncle Al" chemistry" finds quite a few hits. It doesn't really clue me in though, since I decided to stop reading after finding:


http://sci.tech-archive.net/Archive/sci.chem/2006-06/msg00231.html

   This response illustrates as well as anything why I've never
   understood why people take Uncle Al seriously.

   Not that this behavior on Uncle Al's part is anything new --
   he's been promising us the kg-sized diamonds for a decade,
   and his paranoid political rants have achieved near-legendary
   status.


                                Andrew
                                [hidden email]



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