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|Title:||Vitamin B<sub>12</sub> and BF<sub>3</sub>-etherate as catalysts in synthesis of some C<sub>4</sub>-C<sub>12</sub>-alkyl <img src='/image/spc_char/beta.gif'>-D-xylopyranosides|
|Authors:||Petrović, Zorica D|
|Series/Report no.:||<b> Int</b>.<b>Cl</b>.<b><sup>7</sup> C 07</b><b> C</b>|
|Abstract:||Two methods are presented for synthesis of some C<sub>4</sub>-C<sub>12</sub>-alkyl <img src='/image/spc_char/beta.gif'>-D-xylopyranosides. The first method is the vitamin B<sub>12</sub>-catalyzed reaction of glycosylation of acetobromoxylose with alkanols (ROH) (C<sub>4</sub>-C<sub>12</sub>). The reaction is carried out with 2 mol% of vitamin B<sub>12</sub>, with respect to xylosyl bromide, under argon at room temperature. Under these conditions peracetylated C<sub>4</sub>-C<sub>12</sub>-alkyl <img src='/image/spc_char/beta.gif'>-D-xylopyranosides are obtained. Following chromatographic purification these products are de-esterified with a mixture of methanol-triethylamine-water (2:1:1) to give corresponding alkyl <img src='/image/spc_char/beta.gif'>-D-xylopyranosides in 50-60% yield. In all cases 3,4-di-O-acetyl-D-xylal is obtained, as the product of reductive elimination of peracetylated xylosyl bromide (15-25%). The second method is synthesis of C<sub>4</sub>-C<sub>12</sub>-alkyl <img src='/image/spc_char/beta.gif'>-D-xylopyranosides performed by glycosylation of corresponding alkanols with tetra-O-acetyl <img src='/image/spc_char/beta.gif'>-D-xylopyranose in the presence of BF<sub>3</sub>-etherate, as a Lewis acid catalyst. This glycosylation proceeds in only moderate yield (45-55%), but simplicity of this method and avoidance of expensive heavy metal catalysts make such procedure attractive.|
|Appears in Collections:||IJC-B Vol.45B(01) [January 2006]|
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