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Synthesis of β-D galactopyranosyl amino-(N-salicylidene) - 2, 3, 4, 6-tetra-O-acetate as a new chiral Schiff base for asymmetric transformations

Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, Iran
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Molbank 2005, 2005(4), M435; https://doi.org/10.3390/M435
Received: 2 June 2005 / Accepted: 22 September 2005 / Published: 1 October 2005
Carbohydrates constitute a class of inexpensive natural products of high chiral content [1]. They play central roles in the posttranslational biological selectivity [2]. O-Acyl-protected glycosylamines, particularly the 2,3,4,6-tetra-O-pivaloyl-D-galactopyranosylamine and its acetyl derivative are effective chiral auxiliaries in Strecker and Ugi syntheses of α-amino acids[3,4,5].Glycosylamines are valuable intermediates in the preparation of nucleosides and drugs[6,7,8]. Carbohydrate-derived auxiliaries utilize an efficient stereoselective potential in a number of nucleophilic addition reactions on prochiral imines.α-Amino acids, β-amino acids and their derivatives can be synthesized in few synthetic steps, with high enantiomeric purity. A variety of chiral heterocycles can readily be obtained from glycosyl imines by stereoselective transformations [9].The asymmetric Staudinger reaction utilizing 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosylamine as the chiral auxiliary in the synthesis of 2-azetidinones has been reported by us[10]. We now report compound 3 as a new chiral auxiliary Schiff base for β-lactam syntheses.
Molbank 2005 m435 i001
Salicylaldehyde 2 (0.70 g, 0.6ml, 5.73 mmol) was added to a solution of 2,3,4,6-tetra-O-acetyl-β-D-galactosylamine 1 (2.00 g, 5.76 mmol) in ethanol (35 ml). The mixture was refluxed for 5 h. The resulting pale yellow product 3 was collected in 53% yield by filtration.
Melting point: 136-140°C.
IR (KBr, cm-1): 3492.8 (OH); 1745.5 (C=O); 1635.5 (C=N).
1H-NMR (250MHz, DMSO-d6): δ= 12.19(OH, s, 1H); 8.50(NCH, s, 1H); 7.30-6.82(Ar-H, m, 4H); 2.09(OCH3, s, 3H); 2.06(OCH3, s, 3H); 2.01(OCH3, s, 3H); 1.93(OCH3, s, 3H).
13C-NMR (62.9 MHz, DMSO-d6): δ= 169.51-168.55(C=O); 136.05-116.32(Ar); 19.78-19.68(OCH3).
MS (m/z): 451; 331; 169; 109.

Supplementary materials

Supplementary File 1Supplementary File 2Supplementary File 3

Acknowledgment

The authors deeply thank the Shiraz University Research Council for financial support(Grant No.83-GR-SC-31 and 84-GR-SC-23)

References

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  • Sample Availability: Available from MDPI.
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