Donors, hydrogen binding

The chiral catalyst 142 achieves selectivities through a double effect of intramolecular hydrogen binding interaction and attractive tt-tt donor-acceptor interactions in the transition state by a hydroxy aromatic group [88]. The exceptional results of some Diels-Alder reactions of cyclopentadiene with substituted acroleins catalyzed by (R)-142 are reported in Table 4.21. High enantio- and exo selectivity were always obtained. The coordination of a proton to the 2-hydroxyphenyl group with an oxygen of the adjacent B-0 bond in the nonhelical transition state should play an important role both in the exo-endo approach and in the si-re face differentiation of dienophile. 

Methods that deduce a pharmacophore, an arrangement in 3D space of features that contribute or detract from binding and look for its presence in the database that is searched. This method places emphasis on features like hydrogen bond donors, hydrogen bond acceptors, acidic or basic units and hydrophobic fragments and opens the possibility of identifying unexpected scaffolds with required features (pharmacophore-based VS or PHBVS). 

Naphthalimide can be reduced to the corresponding radical anion. Compared to naphthalimide, its radical anion exhibits high hydrogen binding affinity with hydrogen donors. By using these properties of naphthalimide, a molecular shuttle based on... 

Since they have both a vacant low-energy orbital and a lone pair, silylenes might behave either as electron pair donors or acceptors. There is scant evidence for silylenes reacting as Lewis bases, but complexes of silylenes acting as Lewis acids are now well-established these complexes can also be described as silaylides, R2>Si —B+262. Trinquier has calculated that even SiLL should form a weak complex with 112S i , in which a silane hydrogen binds to the p-orbital of the silylene263. 

Pharmacophore keys are 3-D structural keys that are based on features of a molecule that are thought to have relevance for receptor binding. The features typically include hydrogen bond donors, hydrogen bond acceptors, charged centers, aromatic ring centers and hydrophobic centers. Pharmacophore keys are usually based on combinations of three or four pharmacophoric features and their associated distances. Flexibility can be taken into account by combining the keys for all distinct conformations of a molecule. 

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