New branched carbohydrate building block from a tandem elimination-Farvorski rearrangement

Abstract

3-Methoxycarbonyl-1,5-anhydro-β-D-erythro-pentofuranose 1 was obtained when 2,3,4-tri-O-tosyl-1,6-anhydro-β-D-glucopyranose 2 was treated with NaOMe.

References

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7. Selected data for 1: δ_H(CDCl₃) 5.65 (d, 1H, J_1,2exo 2.0, H-1), 5.0 (d, 1H, J_4,5 2.7, H-4), 3.6 (s, 3H, OMe), 3.5 (m, 2H, H-5a and H-5b), 2.7 (dd, 1H, J_2endo,3 8.5, J_2exo,3 4.5, H-3), 2.1 (ddd, 1H, J_2exo,2endo 12.0, H-2exo), 2.0 (dd, 1H, H-2endo); δ_H(CDCl₃) 172.6 (C-3′), 100.4 (C-1), 78.1 (C-4), 68.6 (C-5), 52.2 (OMe), 44.7 (C-3), 36.6 (C-2).
8. Typical procedure: To tritosylate 2(2.35 g) in CHCl₃(25 ml) was added a solution of Na (400 mg) in MeOH (3 ml). The strongly exothermic reaction was left for 30 min. and then water (15 ml) and sat. aq. NH₄Cl (3 ml) was added. The phases were separated and the organic layer dried (MgSO₄), concentrated and the content chromatographed in EtOAc–pentane (1:4) with 1% Et₃N to give 1(261 mg, 44%). In another identical experiment no Et₃N was added to the mobile phase during chromatography. This gave 9 in 49% yield (291 mg).