Carotenoids and related compounds. Part XV. The structure and synthesis of phytoene, phytofluene, ζ-carotene, and neurosporene

Abstract

Structures have been established for the polyenes, phytoene, phytofluene, <-carotene and neurosporene by spectral studies and synthesis. The stereochemistry of these polyenes is discussed.IT is now generally accepted2'3 that phytoene, phytofluene, <-carotene, and neurosporene are intermediates in the biosynthesis of carotenoids, rather than artefacts or by-products of this process.4~~ Each is believed to be converted into the next member of the series 1

The dehydrogenation sequence leading to coloured carotenoids in photosynthetic bacteria

“…The possibility that the R. rubrum heptaene has its chromophore located unsymmetrically in the molecule is strengthened by the close agreement between its absorption spectrum and that reported for a synthetic unsymmetrical isomer of c-carotene (Davis et al 1966).…”

“…The structures ofthe intermediates were established by unambiguous synthesis (Davis, Jackman, Siddons & Weedon, 1961, 1966; the symmetrical structure of g-carotene (7,8,7',8'-tetrahydrolycopene) implies that the dehydrogenation steps occur alternately to the left and to the right of the central chromophore.…”

Nuclear Magnetic Resonance Spectrum of Phytoene

“…1 3 (18). These assignments are based on the spectra of the polyisoprenoid chains in naphtoquinone7) and carotenoids, 5,8) and also on a cyclic triene.9) In the present experiment, the fine structure of the -CH= protons was not well resolved, possibly because of the large size of the phytoene molecule. However, the NMR spectrum is in good agreement with the structure of phytoene.…”

Piperine-Type Amides: Review of the Chemical and Biological Characteristics

“…The C 6 unit, 6-(tetrahydro-2'-pyranyloxy)-1-hexanol, was prepared from 1,6-hexanediol and tetrahydropyran, and oxidizing with pyridinium chlorochromate to the corresponding aldehyde. This gave a 95 % yield of the product .To obtain the C 4 unit methyl crotonate was brominated with N-bromosuccinimide (NBS) (Wohl-Ziegler reaction) to give methyl 4-bromocrotonate (92% yield), which was converted with triethyl phosphite to diethyl-3-methoxycarbonyl-2-propenylphosphonate in 77 % yield (Davis, Jackman, Siddons, & Weedon, 1966;Morrison & Boyd, 2006;Miyakado & Yoshioka, 1979). The 2,4-dienoate was prepared by condensation of the aldehyde with the phosphonate in the presence of sodium methoxide, whose configurations were predominantly trans at C-2 and exclusively trans at C-4.…”