Molbank 2005, M435

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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

A. A. Jarrahpour^*, P. Alvand, R. Arab and A. Beheshti

Chemistry Department, College of Sciences, Shiraz University,

Shiraz 71454, Iran.

Tel: + 98 711 2284822, Fax: +98 711 2280926, e-mail: [email protected] and [email protected]

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[3-5].Glycosylamines are valuable intermediates in the preparation of nucleosides and drugs[6-8]. 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.

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.

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

1. Kunz, H.; Pfrengle, W., Tetrahedron 1988, 44, 5487.

2. Sharon, N.; Lis, H. Chem. Eng. News 1981, 59, 21.

3. Kunz, H.; Pfrengle, W., Angew. Chem. Int. Ed. Engl. 1989, 28, 1067.

4. Kunz, H.; Pfrengle, W., J. Am. Chem. Soc. 1988, 110, 651.

5. Kunz, H.; Sager, W., Angew. Chem. Int. Ed. Engl. 1987, 26, 557.

6. Babiano, R.; Fuentes Mota, J., Carbohydr. Res. 1986, 154, 280.

7. Cusack, N. J.; Hildick, B. J.; Robinson, D. H.; Rugg, P. W.; Shaw, G., J. Chem. Soc., 1973, 1720-1731

8. Cusack, N. J.; Robinson, D. H.; Rugg, P. W.; Shaw, G.; Lofthouse, R., J. Chem. Soc. 1974, 73-81.

9. Kunz, H. In Modern Amination Methods; Ricci, A., Ed.; WILEY-VCH: Weinheim, 2000; pp103.

10. Jarrahpour, A. A.; Shekarriz, M.; Taslimi, A. Molecules 2004, 9, 29

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