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.