294
2
General Synthetic Methods
⊡ Figure 19
Synthesis of a representative oxolane anhydrosugar
⊡ Scheme 25
of 3,6-anhydrofuranoses—has been synthesized from the stannyl intermediate. Compound 86,
readily obtained in a few steps from D-glucurono-3,6-lactone, was converted into chloride
87. The S N 2 displacement of the chlorine with the tin anion [Bu 3 Sn (−) generated from
Bu 3 SnSiMe 3 by action of fluorides] afforded the stannyl derivative 88, which reacted with
benzoyl chloride to give ketone 89 finally transformed into 90 ( > Scheme 25) [57].
Among tetrahydropyran anhydrosugar derivatives the most common are 3,6-anhydro-pyranoses. An example illustrating the synthesis of such types of compounds is the preparation of methyl 3,6-anhydro-β-D-glucoside from methyl 2,3,4-tri-O-acetyl-6-bromo-6-deoxyβ-D-gluco-pyranoside upon treatment with barium hydroxide. 3,6-Ahydro-D-galactose and
3,6-ahydro-D-mannose are prepared in a similar way ( > Fig. 20).
⊡ Figure 20
Examples of 3,6-anhydropyranoses
2
General Synthetic Methods
⊡ Figure 19
Synthesis of a representative oxolane anhydrosugar
⊡ Scheme 25
of 3,6-anhydrofuranoses—has been synthesized from the stannyl intermediate. Compound 86,
readily obtained in a few steps from D-glucurono-3,6-lactone, was converted into chloride
87. The S N 2 displacement of the chlorine with the tin anion [Bu 3 Sn (−) generated from
Bu 3 SnSiMe 3 by action of fluorides] afforded the stannyl derivative 88, which reacted with
benzoyl chloride to give ketone 89 finally transformed into 90 ( > Scheme 25) [57].
Among tetrahydropyran anhydrosugar derivatives the most common are 3,6-anhydro-pyranoses. An example illustrating the synthesis of such types of compounds is the preparation of methyl 3,6-anhydro-β-D-glucoside from methyl 2,3,4-tri-O-acetyl-6-bromo-6-deoxyβ-D-gluco-pyranoside upon treatment with barium hydroxide. 3,6-Ahydro-D-galactose and
3,6-ahydro-D-mannose are prepared in a similar way ( > Fig. 20).
⊡ Figure 20
Examples of 3,6-anhydropyranoses