According to the literature (2, 3, 29), the structure of CB77, without not only vicinal 3,4 hydrogen substitutions but also 2,5-dichloro or 2,3,6 trichloro-phenyl rings, makes it difficult to biotransform to methyl sulfones.
As expected, iodine-for-hydrogen substitution in Tyr3 leads to an increase in lipophilicity of the [68Ga/177Lu]HA-DOTATATE analogs compared to their respective DOTATATE counterparts.
A search of the Cambridge Structural Database indicated that Ltri resulting from nitrogen bound amide hydrogen metal substitution is favoured over chelation through the amide oxygen atom.
The absolute configuration of the corresponding alkanol 4 was controlled efficiently by the chirality resulting from hydrogen isotope substitution of 1 and 2 (Scheme 1).
A structural analysis of the α β interface reveals that three of the L -> H substitutions, αH50P, αL113H and βS128A, lead to three hydrogen bond differences.
Primary antioxidants (e.g., BHA, BHT, TBHQ, tocopherols, and flavonoids) are generally mono- or polyhydroxy phenols with hydrogen-donating substitutions on the ring 6, 19, 24.
Interestingly, the non-hydrogen atom substitutions on substructure at node 25 correspond perfectly to the substituents present in vitamin K (Shearer, 2000).
The SAR analysis of oleanolic acid derivatives modified at C-3 and C-28 indicated that hydrogen-bond acceptor substitution at the C-3 position of oleanolic acid may be advantageous for the improvement of cytotoxicity against PC-3, A549 and MCF-7 cell lines [12].
In addition to direct interference of hydrogen bonding, these substitutions may act indirectly to destabilize hydrogen bond interactions by increasing solvent accessibility.
