A Study of Some cis—trans Isomeric Dehydro-β-carotenes

Dehydro-β-carotene samples obtained from β-carotene constitute mixtures of stereoisomers from which two main crystalline cis forms were isolated. The interconversion of members of this stereoisomeric set was studied by thermic, photochemical and catalytic methods. The mixtures thus obtained contain less of the all-trans compound than in the case of carotenes. One of the observed cis dehydro-β-carotenes showed a degraded spectrum. No distinct cis-peak phenomena were observed in this "retro” system

Action of N-Bromosuccinimide on β-Carotene

β-Carotene when refluxed with N-bromosuccinimide yields a complicated pigment mixture from which three compounds have been isolated in pure state, viz., dehydro-β-carotene, C_(40)H_(54), bisdehydro-β-carotene, C_(40)H_(52), and a pigment very probably identical with anhydro-eschscholtzxanthin, C_(40)H_(50). Some spectral and stereochemical observations are discussed

Conversion of Dehydro-β-carotene, via its Boron Trifluoride Complex, into an Isomer of Cryptoxanthin

Dehydro-β-carotene and BF_3-etherate form a dark blue complex. Cleavage with water (or methanol) resulted in the isolation of a monohydroxy-β-carotene, termed isocryptoxanthin (or its methyl ether). Isocryptoxanthin when treated with acid chloroform undergoes dehydration to yield dehydro-β-carotene which indicates the presence of an allylic hydroxyl group. While naturally occurring cryptoxanthin is 3-hydroxy-β-carotene, isocryptoxanthin is the corresponding 4-compound. Its methyl ether or acetate can also be converted into dehydro-β-carotene

A Study of Some cis—trans Isomeric Dehydro-β-carotenes

Dehydro-β-carotene samples obtained from β-carotene constitute mixtures of stereoisomers from which two main crystalline cis forms were isolated. The interconversion of members of this stereoisomeric set was studied by thermic, photochemical and catalytic methods. The mixtures thus obtained contain less of the all-trans compound than in the case of carotenes. One of the observed cis dehydro-β-carotenes showed a degraded spectrum. No distinct cis-peak phenomena were observed in this "retro” system

Conversion of Dehydro-β-carotene, via its Boron Trifluoride Complex, into an Isomer of Cryptoxanthin

Dehydro-β-carotene and BF_3-etherate form a dark blue complex. Cleavage with water (or methanol) resulted in the isolation of a monohydroxy-β-carotene, termed isocryptoxanthin (or its methyl ether). Isocryptoxanthin when treated with acid chloroform undergoes dehydration to yield dehydro-β-carotene which indicates the presence of an allylic hydroxyl group. While naturally occurring cryptoxanthin is 3-hydroxy-β-carotene, isocryptoxanthin is the corresponding 4-compound. Its methyl ether or acetate can also be converted into dehydro-β-carotene