ChemAxon products import and export SMARTS strings with the following features:
Full-functional (editable) query features
SMARTS features interpreted during import/export as full-functional (editable) query features:
atom lists like [C,N,P] and 'NOT' lists like [!#6!#7!#15]
any bond: ~
ring bond: C@C
hydrogen count: H0, H1, H2, H3, H4
valence: v0, v1, ..., v8
connectivity: X0, X1, X2, X3, X4
in ring: R
ring count: R0, R1, ..., R6
size of smallest ring: r3, r4, r5, r..
number of ring bonds: x2, x3, x4
at least one ring bond: x
aromatic and aliphatic atoms: a, A
aliphatic, aromatic atom query properties
single_or_double, single_or_aromatic, double_or_aromatic bonds (used in Marvin)
directional or unspecified bonds: C\C=C/?C
chiral or unspecified atoms: C[C@?H](Cl)Br
component level grouping: (C).(O) (C.O)
Code: smarts, smiles:s
Features with limited editing support
A subset of SMARTS features are imported as SMARTS atoms/bonds. These atoms/bonds have limited editing support in the Marvin GUI, but can be exported and evaluated (e.g. JChem structure searching handles them correctly):
implicit hydrogen count: h2, h3, h..
degree: D2, D3, D..
more difficult logical expressions in atom or bond expressions: &,;!
(Simpler cases, like atom lists, not lists, "and"-expressions are handled by the above features.)
recursive SMARTS: [$(CCC)]
Features exported as SMARTS atoms/bonds
A subset of features are exported as SMARTS atoms/bonds.
MDL Substitution Count query atom property s<n> is converted to degree Dn. In case of s* the non-H neighbours are counted and exported as degree D<number>.
MDL Unsaturated Atom query atom property u is converted to recursive SMARTS: $([*,#1]=,#,:[*,#1]) is appended after the SMARTS atom.
Implicit and Query Hydrogen Atoms
Impicit Hydrogen atoms are not written inside brackets. Eg: [C:1]
Query Hydrogen atoms are written inside brackets without using the low precedence "and" operator ';'. Eg: [CH3]
Implicit bond types
The default bond types for import and export strongly depend on the atoms connected by the bond.
Aromatic bonds are not written explicitly if neither atoms are aliphatic and they are in a ring.
e.g.: c1ccccc1 But: c:c, c:[c;a], [#6]:c
Single bonds are not written explicitly if at least one atom is not aromatic.
e.g.: CC, C[c;a], Cc, C[C;A], [#6]C But: [#6]-[c;a], c1ccc(cc1)-c2ccccc2
Single_or_aromatic bonds are not written explicitly if both atoms of the bond are aromatic and any of them is not in the same ring.
e.g.: [#6]cc, [#6][c;a], [#6][#6]
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