Das Mischpotential und seine Berücksichtigung bei der Konstruktion von elektrometrischen Flächen

✍ Scribed by B. Milí ević

• Publisher: John Wiley and Sons
• Year: 1963
• Tongue: German
• Weight: 273 KB
• Volume: 46
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19630460226

✦ Synopsis

2R, 4'R, 8'R)-and (ZS, 4'R, 8'R)-a-tocopherol have been synthesized by WITTIG reaction of the two enantiomeric S-(+)and R-(-)-6-acetoxy-Z-formyl-2,5,7, 8-tetramethyl-chromans (I) with (3R, 7R)-hexahydrofarnesyl-triphenylphosphonium bromide (11), followed by hydrogenation and hydrolysis. (2R, 4'R, S'R)-a-tocopherol proved to be identical in every respect with natural so called &-tocopherol. Resolution of the chroman component was achieved via the diastereomeric quinine salts of 2-carboxyethynyl-6-hydroxy-2,5,7,8-tetramethyl-chroman (XVIII), followed b y transformation of the enantiomers into S-(+)and R-(-)-I, respectively.