Reactions and Transformations - Design and Use of Relational Databases in Chemistry - page 105

The unimolecular form of the xform function will not properly work
with this SMIRKS. Instead, an alternate form that requires an array of
SMILES is used. The following SQL
Select xform(ARRAY['CC(=O)Cl','CNC'],
'[C:2]([O,Cl:3])=[O:4].[N:6][H:99]>>[N:6][C:2]=[O:4].[*:3][H:99]');
returns CC(=O)N(C)C.Cl. With this xform function, it is possible to eas-
ily create combinatorial libraries from tables of reactants in the database.
The following SQL will produce 100 products by combining 10 secondary
amines and 10 acid chlorides from the table nci.structures .
select amine.smiles, acid.smiles, xform
(ARRAY[amine.smiles,acid.smiles],
'[H:99][N:1].[C:2](=[O:4])[Cl:3]>>[N:1][C:2]=[O:4]') from
(select smiles from structure where
matches(smiles,'C[NH1]') limit 10) amine,
(select smiles from structure where
matches(smiles,'C(=O)Cl') limit 10)acid;
This SQL statement can be expanded in many different ways to satisfy many
different requirements. For example, an additional where clause in the sub-
select statements could limit selection of reactants by molecular weight, cost,
availability, etc. The type of amine or acid chloride could also be selected
by changing the SMARTS in the matches function. For example, aromatic
amines could be selected by using matches(smiles, 'c[N H1]') .
It is possible to create a table containing many different SMIRKS and
select the appropriate one by name. For example:
select amine.smiles, acid.smiles,
xform(ARRAY[amine.smiles,acid.smiles], smirks) from
(select smiles from structure where
matches(smiles,'C[NH1]') limit 10) amine,
(select smiles from structure where
matches(smiles,'C(=O)Cl') limit 10) acid,
smirks_lib where smirks_lib.name='Schotten-Baumann';
Many other uses of the xform function are possible. Because the function
is an extension of SQL, it can be easily used with all the other features of
the SQL language and capabilities of an RDBMS.
There is no limit on the number of reactants or products that can be
used in SMIRKS. The Ugi reaction 3 is a four-component condensation reac-
tion combining an aldehyde, amine, carboxylic acid, and an isocyanide.
The SMIRKS representing this transformation is [*:1][C:10](=[O:11]).[*:2]
[N:20]([H:21])[H:22].[*:3][C:30](=[O:31])[O:32][H:33].[*:4][N+:40]#[C-:41]>>[*:3]
[C:30](=[O:31])[N:20]([*:2])[C:10]([*:1])[C+0:41](=[O:32])[N+0:40]([H])[*:4]. In
previous examples, every reactant atom was accounted for in the product.