Novel tocopherol derivatives. Part 32: On the bromination of pyrano[3,2-f]chromenes related to γ-tocopherol
摘要:
While bromination of gamma-tocopherol (2) with elemental bromine affords 5-bromo-gamma-tocopherol quantitatively (3), the analogous reaction of its truncated model compound, 2,2,7,8-tetramethylchromanol (2a) is known to be accompanied by side reactions and to produce hitherto unknown byproducts. These compounds originate from pyrano[3,2-f]chromene (6), a byproduct in the synthesis of model compound 2a, which affords bromochromene 7 as the major product. The reaction mechanism was shown to proceed via chromene 8 and its 1,2-dibromo addition compound 9, which eliminates HBr in an E1 process to finally afford 7. Analytical data including crystal structures of both 6 and 7 are reported. (C) 2011 Elsevier Ltd. All rights reserved.
the 5a-bromo derivative by an oxidation/addition mechanism via the corresponding o-quinone methide becomes a competitive process. By measurement of product ratios at different temperatures, the relative and absolute activation energies of the reaction systems with parallel reactions going on (β- and δ-tocopherol) were established. The kinetic data were in very good agreement with DFT results that showed
The invention relates to novel chroman derivatives, stereoisomers and pharmaceutically acceptable salts of Formula I
wherein the substituents are as defined in the specification. They are useful in the treatment of disorders mediated by lipoxygenase, such as immune diseases, respiratory diseases and cardiovascular diseases, as well as in the treatment of neurodegenerative disorders and/or mitochondrial disorders. They are also useful in the manufacture of pharmaceutical formulations for the treatment of such conditions.
The invention relates to novel chroman derivatives, stereoisomers and pharmaceutically acceptable salts of Formula I
wherein the substituents are as defined in the specification. They are useful in the treatment of disorders mediated by lipoxygenase, such as immune diseases, respiratory diseases and cardiovascular diseases, as well as in the treatment of neurodegenerative disorders and/or mitochondria) disorders. They are also useful in the manufacture of pharmaceutical formulations for the treatment of such conditions.
Bromination of the ethano-dimer of alpha-tocopherol (6) afforded pyrano-spirodimer of alpha-tocopherol (7) quantitatively, while the methano-dimer of alpha-tocopherol (10) produced a mixture of products, including the furano-spirodimer 11, pyrano-spirodimer 7, and 5-bromo-gamma-tocopherol (12), the latter two formed in ail unusual dealkylative fragmentation step. The mechanisms were studied by a combination of trapping reactions as well as kinetic and computational studies. (c) 2005 Elsevier Ltd. All rights reserved.