Dataset Information

Remarkable regioselective position-10 bromination of bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a.

ABSTRACT: Both bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a on reacting with NBS (N-bromosuccinamide) undergo electrophilic bromination to provide 10-bromo analogs. The electronic nature of the substituents present at position-3 did not make any difference in the regioselective outcome of the brominated products. These relatively stable brominated chlorins and bacteriochlorins provide an easy way of introducing a wide variety of functionalities, which could be extremely useful in developing improved agents for biomedical applications and supramolecular chemistry.

SUBMITTER: Ethirajan M

PROVIDER: S-EPMC3076286 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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Remarkable regioselective position-10 bromination of bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a.

Ethirajan Manivannan M Joshi Penny P William White H WH Ohkubo Kei K Fukuzumi Shunichi S Pandey Ravindra K RK

Organic letters 20110321 8

Both bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a on reacting with NBS (N-bromosuccinamide) undergo electrophilic bromination to provide 10-bromo analogs. The electronic nature of the substituents present at position-3 did not make any difference in the regioselective outcome of the brominated products. These relatively stable brominated chlorins and bacteriochlorins provide an easy way of introducing a wide variety of functionalities, which could be extremely useful in devel ...[more]

PMID: 21417431

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Project description:BackgroundSeveral papers described the structure of curcumin and some other derivatives in solid and in solution. In the crystal structure of curcumin, the enol H atom is located symmetrically between both oxygen atoms of the enolone fragment with an O···O distance of 2.455 Å, which is characteristic for symmetrical H-bonds. In the solution, the geometry of the enolone fragment is attributed to the inherent disorder of the local environment, which solvates one of the basic sites better than the other, stabilizing one tautomer over the other. In this paper, how the position of methoxy groups in dimethoxy curcuminoids influence the conformation of molecules and how the halogen atoms change it when they are bonded at ?-position in keto-enol part of molecules is described.ResultsSix isomers of dimethoxy curcuminoids were prepared. Conformations in solid state, which were determined by X-ray single crystallography and 1H MAS and 13C CPMAS NMR measurements, depend on the position of methoxy groups in curcuminoid molecules. In solution, a fast equilibrium between both keto-enol forms exists. A theoretical calculation finding shows that the position of methoxy groups changes the energy of HOMO and LUMO. An efficient protocol for the highly regioselective bromination and chlorination leading to ?-halogenated product has been developed. All ?-halogenated compounds are present mainly in cis keto-enol form.ConclusionsThe structures in solid state of dimethoxy curcuminoids depend on the position of methoxy groups. The NMR data of crystalline solid samples of 3,4-diOCH3 derivative, XRD measurements and X-ray structures lead us to the conclusion that polymorphism exists in solids. The same conclusion can be done for 3,5-diOCH3 derivative. In solution, dimethoxy curcuminoids are present in the forms that can be described as the coexistence of two equivalent tautomers being in fast equilibrium. The position of methoxy groups has a small influence on the enolic hydrogen bond. Theoretical calculations show that the energy gap between HOMO and LUMO depend on the position of methoxy groups and are lower in solution. Chlorination and bromination on ?-position of 1,3-diketone moiety do not change the preferential form being cis keto-enol as in parent compounds.

Dataset Information

Remarkable regioselective position-10 bromination of bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a.

Publications

Remarkable regioselective position-10 bromination of bacteriopyropheophorbide-a and ring-B reduced pyropheophorbide-a.

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