ChemInform Abstract: Optically Active 4,5-Epoxy-4,5-dihydro-α-ionones; Synthesis of the Stereoisomeric 4,5 :4′,5′-Diepoxy-4,5,4′,5′-tetrahydro-ε,ε-carotenes and the Steric Course of Their Hydrolysis.
Abstract
Epoxidation of ( +)-α-ionone (I) gives predominantly the cis-epoxide (II) and only small amounts of the trans-epoxide (III).
ChemInform Abstract
Epoxidation of ( +)-α-ionone (I) gives predominantly the cis-epoxide (II) and only small amounts of the trans-epoxide (III). Acid hydrolysis of (II) or (III) affords a single 4,5-glycol (IV), whose structure is established by X-ray analysis of its racemic form (±)-(IV) [space group P21/c] and the reference compound (-)-(V) [space group P2,2,2,]. Racemic α-ionone (±)-(I) is transformed in 5 steps to a mixture of the (±)-cis/trans-C,yphosphonates (VII), which on Wittig reaction with the dialdehyde (VIII) afford a mixture of the diepoxy-gs-carotenes (IX) and (X), which are also obtained as sole compounds in their racemic or optically active forms. Acid hydrolysis of the (6R,6′R)-cis/cis-epoxycarotenoid (IXb) or its trans/ trans analogue (Xb) yields the same tetrol (XI). The racemic form (±)-(XI) of this tetrol is also obtained by an independent synthesis from (±)-(IV).
