@article { ISI:000227933800013, title = {Benzoyl transfer reactivities of racemic 2,4-Di-O-acyl-myo-inosityl 1,3,5-orthoesters in the solid state: molecular packing and intermolecular interactions correlate with the ease of the reaction}, journal = {Chemistry-A European Journal}, volume = {11}, number = {7}, year = {2005}, month = {MAR}, pages = {2103-2110}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}, abstract = {

Racemic 2,4-di-O-acyl-myoinosityl 1,3,5-orthoesters undergo transesterification catalyzed by sodium carbonate with varying ease of reaction in the solid state; reactions in solution and melt do not show such varied differences. An interesting crystal of a 1:1 molecular complex of highly reactive racemic 2,4-di-O-benzoyl-myo-inosityl 1,3,5-orthoformate and its orthoacetate analogue exhibited better reactivity than the latter component alone. Single-crystal X-ray structures of the reactants have been correlated with the observed differences in the acyl-transfer efficiencies in the solid state. Although each of the derivatives helically self-assembles around the crystallographic 2(1) axis linked through O-(HO)-O-... hydrogen bonding, the pre-organization of the reactive groups (C=O [El] and OH [Nu]), C-(HO)-O-... and the C=H(...)pi interactions are significantly more favourable for the reactive derivatives than the less reactive ones. Bond-length distributions also showed differences; the O-C bond of the axial benzoyl group, which gets cleaved during the reaction, is longer (1.345-1.361 angstrom) relative to the chemically equivalent O-C bond of the equatorial benzoyl group (1.316-1.344 angstrom) in the reactive derivatives. These bond-length differences are not significant in the less reactive derivatives. The overall molecular organization is different too; the strikingly discrete helices, which may be viewed as {\textquoteleft}{\textquoteleft}reaction tunnels{\textquoteright}{\textquoteright} and are held by interhelical interactions, are clearly evident in the reactive derivatives in comparison with the less reactive ones.

}, keywords = {hydrogen bonds, Inositol, solid-state reactions, structure elucidation, transesterification}, issn = {0947-6539}, doi = {10.1002/chem.200400851}, author = {Sarmah, M. P. and Gonnade, Rajesh G. and Shashidhar, M. S. and Bhadbhade, Mohan M.} } @article { ISI:000372848000021, title = {Disruption of native beta-turns: consequence of folding competition between native and orthanilic acid proline-based pseudo beta-turn}, journal = {European Journal of Organic Chemistry}, number = {7}, year = {2016}, month = {MAR}, pages = {1380-1388}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

Five tetrapeptides comprising beta-turn-forming elements and a pseudo beta-turn (C9 H-bonding) based on an SAntPro (orthanilic acid - proline) motif were designed and synthesized. Their extensive conformational investigation by single-crystal X-ray crystallography, solution-state 2D NMR spectroscopic, and nOe-restrained MD simulation studies revealed the formation of C14 or C9 folding and disruption of the native beta-turn (C10 H-bonding) architecture. The striking difference between the psi(psi(2)) angle of {\textquoteleft}{\textquoteleft}i + 2{\textquoteright}{\textquoteright} residues of native beta-turn and designed peptides suggest that formation of the native beta-turn is not favored. The results suggest that other turn-forming motifs can dramatically modulate the stability of the native beta-turn structure.

}, keywords = {Conformation analysis, hydrogen bonds, Peptidomimetics, structure elucidation}, issn = {1434-193X}, doi = {10.1002/ejoc.201501558}, author = {Ingole, Tukaram S. and Vijayadas, Kuruppanthara N. and Chaitanya, K. N. and Kotmale, Amol S. and Gawade, Rupesh L. and Gonnade, Rajesh G. and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} } @article {46689, title = {Five concomitant polymorphs of a green fluorescent protein chromophore (GFPc) analogue: understanding variations in photoluminescence with pi-stacking interactions}, journal = {Acta Crystallographica Section B-Structural Science Crystal Engineering and Materials}, volume = {76}, year = {2020}, month = {OCT}, pages = {850-864}, type = {Article}, abstract = {

The synthetically modified green fluorescent protein chromophore analogue 3,4,5-trimethoxybenzylidene imidazolinone (1) yielded five polymorphs (I, II, III, IV, V) concomitantly irrespective of the solvent used for crystallization. The pentamorphic modification of 1 is solely due to the interplay of iso-energetic weak intermolecular interactions in molecular associations as well as the conformational flexibility offered by a C-C single bond, which connects the electron-deficient moiety imidazolinone with the electron-rich trimethoxybenzylidene group. A common structural feature observed in all the polymorphs is the formation of a {\textquoteleft}zero-dimensional{\textquoteright} centrosymmetric dimeric unit through a short and linear C-H center dot center dot center dot O hydrogen bond engaging phenyl C-H and imidazolinone carbonyl oxygen. However, the networking of these dimeric units showed a subtle difference in all the polymorphs. The 2D isostructurality was observed between polymorphs I, II and III, while the other two polymorphs IV and V revealed only {\textquoteleft}zero-dimensional{\textquoteright} isostructurality. The different fluorescence emissions of Form I (blue) and Forms II to V (yellow) were attributed to the differences in pi-stacking interactions. It shows that one can modulate the photophysical properties of these smart materials by slightly altering their crystal structure. Such an approach will aid in developing new multi-colour organic fluorescent materials of varying crystal structures for live-cell imaging and fluorescent sensing applications.

}, keywords = {green fluorescent protein, hydrogen bonds, isostructurality, photoluminescence, pi-stacking, Polymorphs}, doi = {10.1107/S2052520620010343}, author = {Mali, Bhupendra P. and Dash, Soumya Ranjan and Nikam, Shrikant B. and Puthuvakkal, Anisha and Vanka, Kumar and Manoj, Kochunnoonny and Gonnade, Rajesh G.} }