Synthesis of «-Tocopheryl Glycosides

The therapeutic application of vitamin E is seri­ ously limited by its very low solubility in aqueous phases, and tocopherols cannot be used when in­ stant adm inistration of a strong antiradical and antioxidant agent is needed. To increase solubility in w ater and facilitate perm eability through cellu­ lar m em branes tocopherol can be attached to a carbohydrate moiety [1]. The synthesis of some tocopheryl monoand disaccharide derivatives has been reported earlier [2,3]. The reaction of a-tocopherol (1) and 1,2,3,4,6penta-0-acetyl-y3-D-glucose (2) was carried out at 100 °C in the presence of catalytic am ounts of p-toluenesulfonic acid (PTSA), according to H elf­ erich [4] with continuous rem oval of acetic acid (vacuum, 40 Torr) [2]. Two products in the ratio 4:1 (by !H NM R) were isolated (Scheme 1). The m ajor (m ore polar) one was identified as d-a-tocopheryl 2,3,4,6-tetra-0-acetyl-/?-D-g/wco-pyranoside (3a). The structure was confirm ed by com par­ ison of ’H and 13C N M R data with those recently reported by Lahm ann and Thiem [3]. The less abundant product showed in its ]H and 13C N M R spectra, the presence of only three acetyl groups. Since olefinic signals were also observed [doublet at 5.92 ppm in the proton spectrum and two car­ bon resonances at 116.8 (tertiary) and 145.6 ppm H R2 5a: R = Ac, R1 = H, R2 = OAc , 5b: R = Ac, R1 = OAc, R2 = H