Convergent synthesis of new types of stabilized carotenoid compounds

Abstract

A convergent synthetic method for new types of carotenoid compounds containing phenyl substituents at C(13) and C(13') has been developed by the coupling of allylic sulfone and 2,7-diphenyloct-4-enedials, followed by the double elimination strategy. These carotenoid compounds are fairly stable and legitimate candidates for nanosized molecular wires, which show diverse conductance values according to the electronic nature of the substituent group in the phenyl ring.

Synthetic Strategy for Tetraphenyl‐Substituted All‐E‐Carotenoids with Improved Molecular Properties

“…The synthesis of diacetal 6 of all‐ E polyenedial 4 was designed based on the sulfone‐mediated coupling and olefination strategy (Scheme ). Allylic phenyl sulfone 7 now became the key building block, which would couple with dialdehyde 3 . Diacetal 6 was also planned to be synthesized by the “one‐pot” Julia–Kocienski olefination between allylic benzothiazolyl (BT) sulfone 8 and 2,7‐diphenyl‐2,4,6‐octatrienedial ( 9 ) .…”

Enhanced biological activity of carotenoids stabilized by phenyl groups

“…Two unnatural carotenoids, BAS and BTS, respectively, with anisyl and tolyl substituents at C-13 and C-13 0 position were synthesized by the coupling of allylic sulfone subunit and dialdehyde subunit and the double elimination reaction as previously reported (Kim et al, 2011;Maeng et al, 2010). Structures of carotenoid compounds.…”

“…In previous study, Maeng et al (2010) devised stabilized carotenoids based on the fact that vitamin E with the aromatic phenyl group has a protective effect on carotenoids. The terminal cyclohexene rings of b-carotene were replaced by 4-methylthiobenzene rings, and two more phenyl groups were attached at C-13 and C-13 0 position in the series of the stabilized carotenoids (Kim et al, 2011;Maeng et al, 2010). It was envisioned that these stabilized carotenoids would exhibit improved biological activity such as antioxidation.…”

Systematic Synthesis of Diphenyl‐Substituted Carotenoids as Molecular Wires

“…with C 10 4‐octenedial 7b (1 equiv.) followed by dehydro‐desulfonation would produce the desired carotenoids 2 and 3 . Alternatively, the coupling of dienyl sulfones 5 or 6 (2 equiv.)…”

“…The stereoselective construction of dienyl sulfones 5 and 6 could be the key to success for the stereoselective synthesis of all‐ trans carotenoids 2 and 3 . The indium‐mediated addition of chloroallylic sulfones 11 or 12 containing a phenyl substituent to p ‐(methylthio)benzaldehyde ( 9a ) followed by oxonia‐Cope rearrangement of the resulting homo‐allylic alcohol would be a perfect reaction sequence for the synthesis of dienyl sulfones 5 and 6 , as was the synthesis of dienyl sulfone 4 from chloroallylic sulfone 10 containing a 2‐methyl substituent and p ‐(methylthio)benzaldehyde ( 9a ) . Detailed studies of the systematic synthesis of dienyl sulfones 5 and 6 , the efficient construction of diphenyl‐substituted carotenoids 2 and 3 , and their conductance measurements by STM are presented in this work.…”