Taken together, the data obtained emphasize a significant role of the anil state (solution and film) in the occurrence of tautomers
in equilibrium between two different structures of the same compound.
The previous studies indicate that the keto- tautomer
is the more stable structure in both HNQ [7- 25] and HNQ-azo [26-31] (Fig.
8 min are tautomers
of unchanged rapamycin as confirmed by FAB/ MS.
This analysis can be done with the use of FICTS rules to modify structures by (F) removing small organic fragments, (I) ignoring isotopic labels, (C) neutralizing charges, (T) generating canonical tautomers
, (S) ignoring stereochemistry.
5) Valid QSAR modeling practice requires all chemicals to be structurally consistent by converting tautomers
to unique representations.
Bonda has been teaching the industry about the instability of this and other ingredients for decades, but in this presentation, he focused on diketo tautomers
and diketo triplets and the role they play in the production of singlet oxygen, which is toxic to cells.
The second step in the reaction is noncatalytic and involves reactions of hydrogen peroxide with the a-keto acid and enamine/imine tautomers
, which produces, eventually, the carboxylic acid of L-lysine and the oxidative product of the enamine/imine tautomers
Once the structure is drawn, the program can check for tautomers
, and adjust the bond length and angle according to hybridization simplifying the task of drawing complex structures.
For the first time the values of proton affinities were calculated taking into account the contributions of rare tautomers
of cytosine and guanine and the ir protonated forms.
3] showed the following characteristics: a complex series of signals at 1-4 ppm which we assigned to various aliphatic protons, the number of peaks being doubled because both enol and keto tautomers
were present (Fig.
alkylsilylation of aldohexoses yields four cyclic tautomers
in various amounts.
3] showed the following characteristics: we assigned a complex series of signals at one to four parts per million to the various aliphatic protons, the number of peaks being doubled because both enol and keto tautomers
were present in approximately equal amounts, a multiplet at 6.