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Ketals from acetylenes

The absolute stereochemistry of the C-12 and C-13 oxirane moiety of laureoxolane (157), a colorless unstable bromoether obtained from extracts of Laurencia nipponica, was determined on the basis of a chiral synthesis of 156, a degradative derivative of 157. The C-5 to C-8 unit with two asymmetric centers at C-6 and C-7 of 157 corresponds to (25, 35)-l-benzyloxy-3,4-epoxy-2-butanol (142). Elongation of 142 using butyllithium and copper cyanide followed by the creation of a new epoxide provides 152. Lithium acetylide ethylenediamine complex addition to 152 and subsequent ketalization affords the acetylenic acetonide 153, which is coupled with (2i ,35)-l,2-epoxy-3-benzoyloxypentane (154) to furnish 155. Subsequent five-step transformation of 155 provides 156 [60] (Scheme 37). [Pg.339]


See other pages where Ketals from acetylenes is mentioned: [Pg.76]    [Pg.76]    [Pg.70]    [Pg.69]    [Pg.61]    [Pg.689]    [Pg.689]    [Pg.302]    [Pg.582]    [Pg.330]    [Pg.70]    [Pg.689]    [Pg.233]    [Pg.575]    [Pg.242]    [Pg.179]    [Pg.373]    [Pg.352]   
See also in sourсe #XX -- [ Pg.298 ]




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