Table 1 Synthesis of protected disaccharides

From: Deciphering minimal antigenic epitopes associated with Burkholderia pseudomallei and Burkholderia mallei lipopolysaccharide O-antigens

Entry

Donor (equivalents)

Solventa

4 Å MSb/time (h)

TMSOTf (equivalents)

Product yield (%)c

Ratio α/β d

1

8 (1.3)

DCE

+/21

0.2

15 (30)e

α only

2

8 (2.0)

Et2O

+/1

0.2

15 (43)f

α only

3

8 (1.5)

Et2O

+/8

0.2

15 (78)

α only

4

8 (2.0)

Et2O

−/0.2

0.02

15 (95)

α only

5

9 (2.0)

DCE

+/0.2

0.2

16 (51)

α only

6

9 (2.0)

Et2O

−/0.2

0.01

16 (90)

α only

7

10 (2.0)

DCE

+/0.2

0.2

17 (44)

α only

8

10 (2.0)

Et2O/DCE 5:1g

−/0.2

0.01

17 (58)

α only

9

11 (2.0)

Et2O

−/0.2

0.01

18 (81)

α only

10

12 (2.0)

Et2O

−/0.2

0.01

19 (76)

α only

  1. DCE 1,2-dichloroethane, Et 2 O diethyl ether, MS molecular sieves, TMSOTf trimethylsilyltrifluoromethanesulfonate
  2. aAnhydrous solvent over molecular sieves (~0.05 M)
  3. bWith (+) or without (−) freshly activated powdered molecular sieves
  4. cIsolated yield
  5. dDetermined by 1H NMR
  6. eDisaccharide 20 was isolated as the major compound
  7. fSilylated derivative 21 was isolated in 42% yield
  8. gDCE was added to ensure the solubility of donor
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