A simple and efficient synthesis of norbixin and crocetin diesters is described following the schemes C2 + C2o + C2,=C24 and C3 + C14 + C3 = C20 respectively. By means of the Wittig reaction crocetin di‐aldehyde is condensed with a bromoacetic acid ester and a C14‐dialdehyde with an α‐bromopropionic acid ester. The intermediate tri‐ phenylphosphorane compounds are crystalline and easily isolated in a pure state.
To study the oxidative degradation of p‐carotene to vitamin A in the animal body, a number of possible intermediates have been prepared. Starting with 15,15′‐dehydro‐β‐apo‐12′‐carotenal(C25) vinylogous series of polyene aldehydes and acetates with 25 to 40 carbon atoms have been synthesized by successive enol ether condensations. The synthetic β‐apo‐8′‐carotenal(C30) and β‐apo‐8′‐carotenal(C30) were identical with the permanganate oxidation product of β‐carotene and its corresponding alcohol isolated by KARRER.
A simple and efficient synthesis of lycopene is described based on stepwise lengthening of a symmetrical C10‐dialdehyde as central component. This C10‐dialdehyde is lengthened at both ends, first with vinyl ether and then with propenyl ether, leading to a C20‐dialdehyde which is transformed into crocetin dialdehyde by partial hydrogenation of the central triple bond. By means of a new reaction devised by Wittig, crocetin dialdehyde is condensed at both ends with geranylidene‐triphenylphosphorane and lycopene is obtained according to the scheme C10 + C20 + C10 = C40. This synthetic pigment is identical with pure natural lycopene isolated from tomato juice. The Wittig reaction also allows a new β‐carotene synthesis using the components cyclogeranylidene‐triphenylphosphorane and 8,8′‐dehydro‐crocetin dialdehyde.
Ubiquinone(45) has been synthesized from 5‐methyl‐2, 3‐dimethoxy‐hydroquinone and solanesol, which is a C45 isoprenoid alcohol. Chain‐lengthening of solanesol by one isoprene unit and condensation with 5‐methyl‐2, 3‐dimethoxy‐hydroquinone led to ubiquinone(50). The synthetic ubiquinone(45) proved to be identical with a natural sample from liver of vitamin A deficient rats and synthetic ubiquinone‐(50) with a natural sample from pig heart.
The synthesis of trans‐ and cis‐(7′ R,11′ R)‐phylloquinone, trans‐ and cis‐menaquinone‐2, trans‐ and cis‐(7 R,11 R)‐phytol, and related compounds is described. Natural phylloquinone, isolated from alfalfa, is shown to possess the 2′,3′ ‐trans configuration.
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