Hello Rajarshi,

I still do not feel like I have got the idea...

C1=CC=CC=C1 (another example from Daylight site)
clearly has not implicit single bond between
the first "C" and the "1" following it. In this
example, the first "C" is marked with "1", and
in example you gave (C1CC-2C1CCC-2C),

Is it an option to put the 'ring closure digit'
either after atom or after bond? It is documented
somewhere?

With best regards,

Dmitry



>> We (developers of Indigo cheminformatics toolkit)
>> recently received a bug report on Dingo rendering library
>> by Charlie Zhu. He claims that the following SMILES string
>> was produced by CDK and fails to load in Indigo:
>>
>> [H]OC2=NN(C(=O)C=3C(=O)c1c([H])c([H])c(c([H])c1N([H])C2=3)Cl)C([H])([H])C#Cc4c([H])nc([H])c([H])c4([H])
>>  
>>
>>
>> The problem is the "=3" fragment, which occurs twice,
>> first on symbols 17-18. "3" must be a ring closure index
>> which, as Daylight site
>> (http://www.daylight.com/dayhtml/doc/theory/theory.smiles.html)
>> says, are designated "by a digit immediately following the
>> atomic symbol at each ring closure".
>>
>> In this SMILES string, "3" never follows any atomic symbol
>> (it actually follows the double bond symbol twice), and
>> this is why our SMILES parser rejects this string, and then
>> Dingo raises an error.
> 
> 
> It might be that the Daylight spec refers to the fact that the bond is 
> implicit.
> 
> If an explicit bond is specified then it seems that the ring closure 
> number can come after the bond. For the above case, Daylight Depict will 
> accept the SMILES.
> Another example is
> 
> C1CC2C1CCC2C
> C1CC-2C1CCC-2C
> 
> which Daylight will also accept as valid SMILES.
> 
> I can't find mention of this behavior in the spec - does anybody know if 
> this behavior is specified somewhere?
> 
> ----------------------------------------------------
> Rajarshi Guha        | NIH Chemical Genomics Center
> http://www.rguha.net | http://ncgc.nih.gov
> ----------------------------------------------------
> A motion to adjourn is always in order.


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