Asymmetric syntheses. Part VIII. Asymmetric synthesis of β-allenic alcohols with the lithium aluminium hydride–3-O-benzyl-1,2-O-cyclohexylidene-α-D-glucofuranose complex; determination of the absolute configuration of marasin (nona-3,4-diene-6,8-diyn-1-ol) and 9-methylmarasin (deca-3,4-diene-6,8-diyn-1-ol)

Abstract

The following asymmetric reductions with the lithium aluminium hydride–3-O-benzyl-1,2-O-cyclohexylidene-α-D-glucofuranose complex were carried out. Hex-2-en-4-yn-1-ol gave (–)-hexa-3,4-dienol, [α]D²⁰–10°; hept-2-en-4-yn-1-ol gave (–)-hepta-3,4-dienol, [α]_D²⁰–8.9°; non-2-en-4-yn-1-ol gave nona-3,4-dienol, [α]_D²⁰–7.4°; 5-phenylpent-2-en-4-yn-1-ol gave 5-phenylpenta-2,3-dienol, [α]_D²⁰–16.4°; 8,8-dimethylnon-2-en-4,6-diyn-1-ol gave (–)-8,8-dimethylnona-3,4-dien-6-yn-1-ol, [α]_D²⁵–12.5°; 7-phenylhept-2-en-4,6-diyn-1-ol gave 7-phenylhepta-3,4-dien-6-yn-1-ol, [α]_D²⁵–3.1°; non-2-ene-4,6,8-triynyl-1-ol gave (–)-marasin, [α]_D²⁵–26.6°; and dec-2-ene-4,6,8-triyn-1-ol gave 9-methylmarasin, [α]_D²⁵–11.3°. The absolute configuration of all the β-allenic alcohols thus obtained is deduced as R.