Table 2 Synthesis of protected trisaccharides

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

Entry

Acceptor

Donora

Promoterb

Solventc

T (°C) (time (h))

Product

Yield (%)d

1

22

14

NIS, AgOTf

Et2O/DCE

−10 (0.2)

25

65e

2

23

14

NIS, AgOTf

Et2O/DCE

−10 (0.2)

26

50e

3

20

14

NIS, AgOTf

Et2O/DCE

−10 (0.2)

24

NDf

4

20

14

NIS, AgOTf

DCE

−10 (1)

24

NDf

5

20

14

NIS, AgOTf

DCM

−78 (3)

24

NDg

6

20

14

CuBr2, TBAB

DCM/DMF

22 (72)

27

90

7

20

14

DMTST, DTBMP

DCE

40 (48)

24

NDh

8

20

S26 (F)

SnCl2, AgOTf

Et2O/DCM

−10 (0.3)

24

NDf

9

20

S27 (PTFA)

TMSOTf

DCE

−10 (0.2)

24

NDf

10i

20

S27 (PTFA)

TBSOTf

tol

75 (2)

28

60

  1. AgOTf silver(I) trifluoromethanesulfonate, DCM dichloromethane, DDQ 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, DMF N,N-dimethylformamide, DMTST dimethyl(methylthio)sulfonium trifluoromethanesulfonate, DTBMP 2,6-di-tert-butyl-4-methylpyridine, NIS N-iodosuccinimide, TBAB tetrabutylammonium bromide, TBSOTf tert-butyldimethylsilyl trifluoromethanesulfonate, tol toluene
  2. aDonor was used in excess (1.5 equivalents)
  3. bThe reaction was performed adding freshly activated powdered molecular sieves
  4. cAnhydrous solvent over molecular sieves (~0.05 M)
  5. dIsolated yield
  6. eOnly the β-anomer was detected by 1H NMR
  7. fDegradation of donor
  8. gThe dimer 29 was detected as the major compound
  9. hNo reaction
  10. iInverse procedure
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