DE-A 2851051 describes the preparation of 11-(5,5-dimethyl-1,3-dioxan-2-yl)-2,4,6,8,10-dodecapentaenal by Wittig or Wittig-Horner olefination with 2,6-dimethylocta-2,4,6-triene-1,8-dial with a suitable C5 building block under specific reaction conditions. The disadvantage of this process is, however, that the asymmetric C10 dialdehyde employed is not a synthon which is customary on the industrial scale.
Synth. Met. 42, 1557 (1991) describes the preparation of crocetindial mononeopentyl glycol acetal by partial hydrolysis of crocetindial bisneopentyl glycol acetal. The monoacetal is purified by chromatography. The selectivity of a partial acetal cleavage is normally inadequate, which makes the process described appear undesirable for an industrial process.
J. Chem. Soc., Chem. Commun. 1977, 467 and J. Chem. Soc. Perkin Trans 1 (1988) 1383 describes the preparation of methyl 11-(1,3-dioxolan-2-yl)-2,6-dimethyl-2,4,6,8,10-dodecapentaenoate by acetalization of the aldehyde with ethylene glycol.
USPTO Backgrounds
USPTO Backgrounds