Geranylgeranyl bromide

For the synthesis of phytoene (150) and phytofluene (151) the C20 + C20 = C40 strategy has been applied [85,86], For the preparation of phytoene (150), trans-geranyllinalool (165) was treated with phosphorus tribromide to give geranylgeranyl bromide (166) which was reacted with triphenylphosphine to give the C2o-phosphonium salt 167. The C2o-aldehyde 168 was prepared by treatment of 166 with KOH and 2-nitropropane. The Wittig reaction of 167 and 168 with PrLi gave a mixture of (E/Z)-isomers of phytoene (150) in an overall yield of 6% referred to 165 (Scheme 38). 

The boviquinones-3 and -4 have been synthesised in moderate yields from 2,5-dihydroxy-l,4-benzoquinone and the corresponding allylic bromide in the presence of a tertiary amine (Scheme 40) (389). It is interesting that the success of these reactions was crucially dependent on the direct use of farnesyl bromide and of geranylgeranyl bromide without special purification. The preparation and properties of the chromenols and chromanols of boviquinone-4 have been reported (71). 

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