Compound

[α]D25 in MeOH

Tautomeric composition in D2O, (%)

Form A

Form (2R,4S)

Form (2S,4S)

2a

?89.1, с 1.31

?

95

5

2b

?91.2, с 1.50

?

93

7

2c

?70.1, с 1.50

?

90

10

2d

?97.7, с 1.40

?

93

7

2e

?77.2, с 1.53

?

87

13

2f

?69.5, с 1.50

?

92

8

2g

?60.2, с 2.01

13

68

19

2h

?35.1, с 2.02

51

40

9

2i

?37.2, с 1.70

18

66

16