Water. A New Protocol for the Preparation of Optically Active Norstatines.

Transcription

1 SUPPRTING INFRMATINS First ne-pot Copper-Catalyzed Synthesis of α-hydroxy-β-amino Acids in Water. A New Protocol for the Preparation of ptically Active Norstatines. Francesco Fringuelli,* Ferdinando Pizzo, Mauro Rucci and Luigi Vaccaro* Dipartimento di Chimica, Università di Perugia, Perugia (Italia) Fax: (+39) frifra@unipg.it; luigi@unipg.it CNTENTS page S2 page S2 Experimental Section Measurement of Enantiomeric Excess page S4 Characterization Chart for compound 3 page S5 page S6 page S7 Characterization Chart for compound 9d Characterization Chart for compound 9e Characterization Chart for compound 9g S1

2 Experimental Section CAUTIN Azides can be very explosive compounds and should be handled with great care. During our study we encountered no problems. All chemicals were purchased and used without any further purification. In this work we have used de-ionized water. Ion exchange was performed on Dowex 50WX8-400 and eluted with a 1M NH 4 H aqueous solution prepared using bi-distilled water. rganic solvents were dried by conventional methods, GC analyses were performed with an SPB-5 fused silica capillary column (30 m, 0.25 mm diameter), an on column injector system, a FID detector and hydrogen as the carrier gas. GC-MS analyses were carried out with 70 ev electron energy. Amino acids were analyzed as trimethylslyl derivatives that were prepared following procedures. [1] The β-azido-αhydroxycarboxylic acids were analyzed by GC as methyl ester derivatives obtained by treating them with an ether solution of CH 2 N 2. All 1 H NMR spectra were taken on a 400 spectrometer in D 2 with 1,4-dioxane at 3.75 ppm. All 13 C NMR spectra were taken at MHz in D 2 with 1,4-dioxane at ppm. Chiral HPLC analyses were performed by using a CHIRALCEL D-H column (250 x 46 mm, 5 µm) and an UV detector set at 250 nm. All melting points are uncorrected. The α-hydroxy-β-amino acids 4, 5, 9a-9c and 9f are known in the literature. [2] 3, 9d, 9e and 9g are new compounds and are described below. Measurement of Enantiomeric Excess Epoxy alcohols 4, 5, and 6: Enantiomeric excesses (ees) of 4, 5, and 6 were determined by 1 H NMR analyses of the corresponding Mosher s esters following the same procedure reported by Sharpless et al. 3 ees of epoxy alcohols 4 and 5 were also measured by HPLC analyses using a chiral S2

3 stationary phase. Samples were prepared by dissolving the epoxy alcohol in ethanol (5 mg/ml), injected (5 µl) into the column and eluted with 2/98 (v/v) isopropanol/n-hexane mobile phase at a flow rate of 1.0 ml/min. For comparison racemic mixtures were analyzed under the same conditions. α-hydroxy-β-amino acids 1 and 2: Enantiomeric excesses (ees) of 1 and 2 were determined on their N-Acetyl-methyl ester derivatives (pyridine/acetic anhydride then diazomethane) by HPLC analyses using a chiral stationary phase. Samples were prepared by dissolving the epoxy alcohol in ethanol (5 mg/ml), injected (5 µl) into the column and eluted with 4/96 (v/v) isopropanol/n-hexane mobile phase at a flow rate of 1.0 ml/min. For comparison racemic mixtures were analyzed under the same conditions. 1. C. W. Gerke, K. Leimer J. Chromatogr. 1971, 57, (a) F. Fringuelli, F. Pizzo, L. Vaccaro J. rg. Chem. 2001, 66, and literature cited therein; (b) S. L. Herbeson, S. M. Abelleira, A. Akyiama, R.III Barrett, M. R. Carrell, J. A. Straub, J. N. Tkacz, W. Chichih, G. F. Musso J. Med. Chem. 1994, 37, ; (c) C. W. Jefford, J. McNulty, Z. H. Lu, J. B. Wang Helv. Chim. Acta 1996, 79, ; (d) C. Alemany, J. Bach, J. Farràs, J. Garcia rg. Lett. 1999, 1, ; (e) M. E. Bunnage, S. G. Davies, C. J. Goodwin Synlett 1993, ; (f) I. jima, T. Wang, F. Delaloge Tetrahedron Lett. 1998, 39, Gao Y.; Hanson R. M.; Klunder J. M.; Ko S. Y.; Masamune H.; Sharpless K. B. J. Am. Chem. Soc. 1987, 109, S3

4 compound 3 (-)-(2S,3S)-3-amino-2-hydroxyhexanoic acid n-pr S. L. Herbeson, S. M. Abelleira, A. Akyiama, R.III Barrett, M. R. Carrell, J. A. Straub, J. N. Tkacz, W. Chichih, G. F. Musso J. Med. Chem. 1994, 37, C2 H (+)-(2S,3R)-6 Cu(N 3 ) 2 Cu(B) (s) H H n-pr H (-)-(2S,3S)-3 C 6 H 13 N 3 Mol. Wt.: Method: 10.0 mmol (1.300 g) of a (+)-(2S,3R)-2,3-epoxyhexanoic acid (6) were dissolved in water (10 ml). Powdered NaN 3 (0.975 g, 15 mmol) and 10 ml of an aqueous solution 0.1 M of Cu(N 3 ) 2 were added under stirring (resulting ph ~ 4.3) and warmed to 65 C. After 1.5 h (ph ~ 5.5) the reaction mixture was cooled to 0 C, and NaBH 4 was added portion-wise (0.757 g, 20 mmol). After 30 min the reaction mixture was filtered and the copper boride was separated quantitatively. The aqueous mother liquors were acidified to red (indicator paper) with a few drops of concentrated HCl and charged on an ion-exchange resin Dowex 50WX Eluting with NH 4 H 0.1 M the title compound 3 was isolated after aqueous phase evaporation, in 83 % yield as a white crystalline solid. Mol Formula C 6 H 13 N 3 m.p./b.p. > 220 C decomposition Tlc - R f (solv) 0.65 (MeH/AcH/H 2, 4:1:1) [α] D (c. solv) (c = N HCl) FT-IR (CsI, ν max cm -1 ): 1063 (w), 1387 (w), 1502 (m), 1590 (s), 1629 (m), 2963 (s), 3075 (m), 3442 (m) Elemental Analysis : C ; H. 8.90; N Found: C ; H. 8.87; N D 2, t J = 7.5 Hz 1,4-dioxane m m d J = 3.4 Hz 13 C NMR ( MHz, D 2 ): 12.8, 18.1, 26.2, 53.6, 71.6, m/z (EI, 70 ev): as tris-tms derivative 363 (M +, 2), 292 (19), 144 (100), 73 (38) S4

5 compound 9d Rel(1S,2S)-2-amino-1-hydroxycyclohexanecarboxylic acid H 7d Cu(N 3 ) 2 Cu(B) (s) (rac)-9d C 7 H 13 N 3 Mol. Wt.: Method: 10.0 mmol (1.420) of a (±)-1,2-epoxycyclohexancarboxylic (7d) acid were dissolved in water (10 ml). Powdered NaN 3 (0.975 g, 15 mmol) and 10 ml of an aqueous solution 0.1 M of Cu(N 3 ) 2 were added under stirring (resulting ph ~ 4.3) and warmed to 30 C. After 0.25 h (ph ~ 5.5) the reaction mixture was cooled to 0 C, and NaBH 4 was added portion-wise (0.757 g, 20 mmol). After 30 min the reaction mixture was filtered and the copper boride was separated quantitatively. The aqueous mother liquors were acidified to red (indicator paper) with a few drops of concentrated HCl and charged on an ion-exchange resin Dowex 50WX Eluting with NH 4 H 0.1 M the title compound 9d was isolated after aqueous phase evaporation, in 80% yield as a white crystalline solid. Mol Formula C 7 H 13 N 3 m.p./b.p. > 240 C decomposition Tlc - R f (solv) 0.63 (MeH/AcH/H 2, 4:1:1) [α] D (c. solv) FT-IR ( CsI, ν max cm -1 ): 775 (m), 824 (m), 1089 (m), 1520 (w), 1574 (s), 1646 (s), 2858 (s), 2928(s). Elemental Analysis : C ; H. 8.23; N Found: C ; H. 8.27; N D 2, m 1,4-dioxane m m m dd J = 4.2, 10.9 Hz 13 C NMR ( MHz, D 2 ): 22.9, 23.4, 28.2, 36.1, 57.2, 75.7,178.7 m/z (EI, 70 ev): as tris-tms derivative 375 (M +, 31), 258 (26), 171 (9), 170 (6), 128 (100), 73 (75) S5

6 compound 9e Rel(2S,3S)-3-amino-2-hydroxy-2-methyl-pentanoic acid Et H Me Cu(N 3 ) 2 Cu(B) (s) H H Et Me 7e (rac)-9e C 6 H 13 N 3 Mol. Wt.: Method: 10.0 mmol (1.300 g) of a (±)-2,3-epoxy-2-methylpentanoic acid (7e) were dissolved in water (10 ml). Powdered NaN 3 (0.975 g, 15 mmol) and 10 ml of an aqueous solution 0.1 M of Cu(N 3 ) 2 were added under stirring (resulting ph ~ 4.3) and warmed to 65 C. After 0.25 h (ph ~ 5.5) the reaction mixture was cooled to 0 C, and NaBH 4 was added portion-wise (0.757 g, 20 mmol). After 30 min the reaction mixture was filtered and the copper boride was separated quantitatively. The aqueous mother liquors were acidified to red (indicator paper) with a few drops of concentrated HCl and charged on an ion-exchange resin Dowex 50WX Eluting with NH 4 H 0.1 M the title compuond 9e was isolated after aqueous phase evaporation, in 83% yield as a white crystalline solid. Mol Formula C 6 H 13 N 3 m.p./b.p. > 260 C decomposition Tlc - R f (solv) 0.66 (MeH/AcH/H 2, 4:1:1) [α] D (c. solv) FT-IR ( CsI, ν max cm -1 ): 602 (m), 671 (m), 1122 (s), 1139 (s), 1622 (s), 3412 (s), 3458 (s) Elemental Analysis : C ; H. 8.90; N Found: C ; H. 8.87; N D 2, t J = 7.5 Hz 1,4-dioxane m m dd J = 3.2, 10 Hz 13 C NMR ( MHz, D 2 ): 10.5, 22.4, 22.6, 59.9, 75.8, m/z (EI, 70 ev): as tris-tms derivative 363 (M +, 2), 306 (9), 291 (1), 147 (13), 130 (100), 73 (32) S6

7 compound 9g Rel(2S,3S)-3-amino-2-hydroxy-2-methyl-3-phenylpropanoic acid Ph H Me H Ph H Me 7g Cu(N 3 ) 2 Cu(B) (s) (rac)-9g C 10 H 13 N 3 Mol. Wt.: Method: 10.0 mmol (1.780 g) of (±)-2,3-epoxy-2-methyl-3-phenyl-propionic acid (7g) were dissolved in water (10 ml). Powdered NaN 3 (0.975 g, 15 mmol) and 10 ml of an aqueous solution 0.1 M of Cu(N 3 ) 2 were added under stirring (resulting ph ~ 4.3) and warmed to 65 C. After 3 h (ph ~ 5.5) the reaction mixture was cooled to 0 C, and NaBH 4 was added portion-wise (0.757g, 20 mmol). After 30 min the reaction mixture was filtered. and the copper boride was separated quantitatively. The aqueous mother liquors were acidified to red (indicator paper) with a few drops of concentrated HCl and charged on an ion-exchange resin Dowex 50WX Eluting with NH 4 H 0.1 M the title compound 9g was isolated after aqueous phase evaporation, in 91% yield as a white crystalline solid. Mol Formula C 10 H 13 N 3 m.p./b.p. > 120 C decomposition Tlc - R f (solv) 0.73 (MeH/AcH/H 2, 4:1:1) [α] D (c. solv) FT-IR ( CsI, ν max cm -1 ): 703 (m), 1184 (w), 1403 (m), 1617 (s), 3414 (m) Elemental Analysis : C ; H. 6.71; N Found: C ; H. 6.77; N D 2, s 1,4-dioxane s m 13 C NMR ( MHz, D 2 ): 23.5, 61.2, 77.0, 128.6, 129.4, 129.6, 135.4, m/z (EI, 70 ev): as tris-tms derivative, decomposed S7