| Compound | R | Initial aldose | Form in crystals | Tautomeric composition (%) in DMSOd6 | ||
| Form B | Form A | Form C | ||||
| 4a | H | L-Arabinose | F | - | - | 100 |
| 4b | H | D-Ribose | F | - | - | 100 |
| 4c | CH3 | L-Rhamnose | F, B | 35 | 20 | 45 |
| 4d | CH2OH | D-Galactose | F | - | - | 100 |
| 4e | CH2OH | D-Glucose | F, B | 45 | - | 55 |
| 4f | CH2OH | D-Mannose | F | 35 | 15 | 50 |