Carotenoids and related polyenes. Part 3. First total synthesis of fucoxanthin and halocynthiaxanthin using oxo-metallic catalyst

Syntheses of allene-modified derivatives of peridinin toward elucidation of the effective role of the allene function in high energy transfer efficiencies in photosynthesis

“…3). Both half-segments would be synthesized from the optically homogenous epoxyaldehyde derivative 9 12 and (−)-vinyltriflate 10 , 3 b , c both of which had been prepared from (−)-actinol. The outline of the synthesis of ylidenbutenolide segment 5 is described in Scheme 1 as reported previously.…”

“…The first total synthesis of enantiomerically pure peridinin was achieved by Ito et al in 1990. 3 We reported the second total synthesis of peridinin in 2002, featuring high stereochemical control of the six asymmetric carbons and the geometry of the seven double bonds in the molecule. 4 The third total synthesis was described by Brückner’s group in 2006, employing a novel strategy using (+)-diethyl tartrate and (−)-actinol, 5 and the fourth one was achieved by de Lera’s group in 2007, featuring three-component coupling using a dihalogenated C 8 linchpin unit.…”

Highly Efficient Stereocontrolled Total Synthesis of the Polyfunctional Carotenoid Peridinin

“…A mixture of allyl ester 18 (Scheme 4) and vinyl iodide 11 (Scheme 3, 1 equivalent) was stirred in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium and cuprous iodide in triethylamine at room temperature for 1 h. After the complete consumption of 18 was ascertained by TLC, formic acid was added to the reaction mixture at room temperature, and the resulting mixture was stirred for 20 h. As expected, we obtained the desired ylidenebutenolide 3 in 49 % yield as a single stereoisomer. Sonogashira coupling of 18 with 11, reductive deallylation, [19] and highly stereoselective intramolecular lactonization proceeded successfully via 19 in one pot [20] by the successive action of Pd 0 and Pd II catalysts.…”

“…After several trials, we knew that the halides derived from the C 17 -allene segment 2 were unstable under the reaction conditions required for the preparation of the corresponding Wittig salt, although the very similar C 15 -Wittig salt has been reported. [20] We thus turned our attention to the modified Julia ± Kocienski olefination, [21] which made the olefination possible at a relatively lower temperature. Allene 2 was transformed into benzothiazole sulfone 21 by the Mitsunobu reaction with 2-mercaptobenzothiazole, followed by molybdenum(vi)-catalyzed oxidation [22] (Scheme 6).…”

Tris(triphenylsiloxy)vanadium Oxide

“…While linear propargylic alcohols generate α,β-unsaturated carbonyl compounds, cyclohexanol derivatives generally give a mixture of α,β-and β,γ-unsaturated carbonyl compounds under similar conditions (eq 2). 3 The β,γ-unsaturated product is likely derived from the E-olefin isomer of the initial product mixture through an intramolecular prototropic rearrangement. In certain cases, the reaction could be highly regioselective for the formation of the nonconjugated isomer.…”