Wednesday, March 27, 2013

So How Exactly Does Docetaxel E7080 Perform?

Enantiomers 1 and Docetaxel 3, which have the methyl substituent along with the base on the same side on the ring plane, show a clear preference for getting the methyl substituent in an equatorial position along with the deazapurine moiety in an axial position.

Interestingly, the signal for piperidine ring C3 H of 1 was noted at 4. 78 ppm whilst the C3 H of 2 was found at 4. 32 ppm. The relative downfield shift in 1 hugely suggests a additional equatorial character to the C3 H of 1 and relative axial character to the C3 H of 2, Docetaxel which is consistent with the results from the MCMM searches. Using the deazapurine base as the anchor point for discussion it is clear that even the fairly minor change of the stereochemical configuration of the methyl group in structures 1 and 2 results in significant changes in the ultimate three dimensional structures of these agents. This broadly accepted phenomenon is intensified when placing chiral substituents on five and six member ring structures due to hypersensitivity in ring conformations.

The NSCLC opening of the cleft is defined by hydrophilic residues like Arg953, Asn954, Asp949 and Gln988. Interactions with residue backbones of the hinge region define the binding motif of many kinase inhibitors. We, therefore, utilized specified hydrogen bonds between Glu903 and Leu905 and each stereoisomer as a criterion for retrieving the ligand poses from the docking results along with the docking score and the energetic contributes to the binding interactions. The results from the highest scoring Jak3 1 docking complex are shown in Figure 5 and illustrate that the N1 and N7 nitrogens of the deazapurine moiety participate in key hydrogen bonds with residues Glu903 and Leu905. These interactions mimic hydrogen bonds found within the crystal structure of Jak3 with AFN941.

For 2, the six member ring assumes a half chair Docetaxel conformation with both the substituent in equatorial position. Compound 3 docked with the six member ring in a chair conformation and, contrary to the conformational preferences revealed by the MCMM search, the methyl and base substituents were found in the axial and equatorial position, respectively.

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