Peptide Synthesis
3714±3721
coupling was used with: l-alanine-tert-butyl ester hydrochloride (75 mg,
0.41 mmol), NEt3 (41 mg, 57 mL, 0.41 mmol), AGalOC-phenylalanine acid
13 (183 mg, 0.34 mmol) in dry CH2Cl2 (15 mL), and EEDQ (168 mg,
0.68 mmol) in dry CH2Cl2 (3 mL). The b-dipeptide 16 (152 mg, 67%) was
isolated as a white foam. M.p. 82 ± 858C; Rf 0.43 (ethyl acetate/hexane
2:1); [a]D22 12.8 (c 1.0 in CHCl3); 1H NMR (250 MHz, CDCl3): d
7.32 ± 7.28 (m, 3H), 7.22 ± 7.16 (m, 2H), 6.28 (m, 1H), 5.63 (d, J 8.3 Hz,
1H), 5.53 (d, J 8.0 Hz, 1H), 5.40 (d, J 3.1 Hz, 1H), 5.30 (dd, J 10.3,
8.4 Hz, 1H), 5.06 (dd, J 10.3, 3.2 Hz, 1H), 4.35 (quint, J 7.1 Hz, 1H),
4.18 ± 4.13 (m, 2H), 4.10 ± 4.05 (m, 2H), 3.13 (dd, J 13.8, 6.2 Hz, 1H), 3.03
(dd, J 13.7, 6.8 Hz, 1H), 2.15 (s, 3H), 2.04 (s, 3H), 2.02 (s, 3H), 1.97
(s,3H), 1.43 (s, 9H), 1.30 (d, J 7.1 Hz, 3H); 13C NMR (125 MHz, CDCl3):
d 171.5, 170.3, 170.1, 169.9, 169.7, 169.4, 153.3, 135.5, 129.3, 128.7, 127.2,
93.4, 82.1, 71.3, 70.8, 67.6, 66.7, 60.8, 56.1, 48.7, 38.4, 27.8, 20.7, 20.5, 18.5;
N-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyloxycarbonyl)-l-leucyl-l-
serine tert-butyl ester (20): The general procedure for dipeptide coupling
was used with: l-serine-tert-butyl ester (60 mg, 0.37 mmol), AGalOC-
leucine acid 14 (168 mg, 0.33 mmol), EDC (79 mg, 0.40 mmol), and HOBt
(76 mg, 0.50 mmol) were added to the reaction flask, the mixture was
cooled (08C); and DMF (10 mL) was added. The b-dipeptide 20 (89 mg,
40%) was isolated as a colorless oil. Rf 0.19 (ethyl acetate/hexane 1:1);
[a]D24 5.3 (c 1.5 in CHCl3); 1H NMR (500 MHz, CDCl3): d 6.83 (d,
J 7.3 Hz, 1H), 5.62 (d, J 8.3 Hz, 1H), 5.47 (d, J 7.8 Hz, 1H), 5.42 (d,
J 2.9 Hz, 1H), 5.30 (dd, J 10.4, 8.4 Hz, 1H), 5.08 (dd, J 10.4, 3.3 Hz,
1H), 4.49 (dt, J 7.3, 3.3 Hz, 1H), 4.20 (m, 1H), 4.18 ± 4.10 (m, 2H), 4.0 ±
4.04 (m, 1H), 3.91 (dd, J 11.3, 3.2 Hz, 1H), 3.88 (dd, J 11.3, 3.8 Hz, 1H),
2.88(brs, 1H), 2.15 (s, 3H), 2.07 (s, 3H), 2.03 (s, 3H), 1.98 (s, 3H), 1.69 ± 1.49
(m, 3H), 1.47 (s, 9H), 0.95 (d, J 4.6 Hz, 3H), 0.93 (d, J 4.6 Hz, 3H);
13C NMR (125 MHz, CDCl3): d 171.8, 170.4, 170.1, 170.0, 169.9, 153.9,
93.6, 82.9, 71.4, 70.8, 67.8, 66.8, 63.3, 60.9, 55.4, 53.9, 41.3, 28.0, 24.6, 22.9,
HRMS (FAB-3-NBA) [MH] : calcd 667.2714; found 667.2551; elemental
analysis calcd (%) for C31H42N2O14: C 55.85, H 6.35, N 4.20; found C 55.52,
H 6.35, N 3.90.
21.8, 20.7, 20.6, 20.5; HRMS (FAB-3-NBA) [MH] : calcd 649.2820; found
649.2848.
N-(2,3,4,6-Tetra-O-acetyl-d-galactopyranosyloxy-carbonyl)-l-phenylalan-
yl-l-serine tert-butyl ester (17): The general procedure for dipeptide
coupling was used with: l-serine-tert-butyl ester (60 mg, 0.37 mmol),
AGalOC-phenylalanine acid 13 (181 mg, 0.34 mmol) in dry CH2Cl2
(10 mL), and EEDQ (126 mg, 0.51 mmol) in dry CH2Cl2 (5 mL). The b-
dipeptide 17 (92 mg,40%) was isolated as a white wax. Rf 0.33 (ethyl
acetate/hexane 2:1); [a]2D4 21.2 (c 1.0 in CHCl3); 1H NMR (500 MHz,
CDCl3): d 7.31 ± 7.18 (m, 5H), 6.65 (d, J 6.8 Hz, 1H), 5.62 (d, J 8.3 Hz,
1H), 5.55 (d, J 7.6 Hz, 1H), 5.40 (d, J 3.2 Hz, 1H), 5.28 (dd, J 10.4,
8.3 Hz, 1H), 5.07 (dd, J 10.4, 3.4 Hz, 1H), 4.43 ± 4.39 (m, 2H), 4.16 ± 4.09
(m, 2H), 4.04 (d, J 6.8 Hz, 1H), 3.91 (dd, J 11.4, 3.1 Hz, 1H), 3.82 (dd,
J 11.4, 4.0 Hz, 1H), 3.10 (dd, J 6.7, 3.8 Hz, 2H), 2.15 (s, 3H), 2.06 (s,
3H), 2.02 (s, 3H), 1.98 (s, 3H), 1.45 (s, 9H); 13C NMR (125 MHz, CDCl3):
d 170.4, 170.3, 170.1, 169.9, 168.8, 153.5, 135.6, 129.2, 129.0, 128.9, 127.4,
93.6, 83.0, 71.4, 70.8, 67.7, 66.7, 63.3, 60.9, 56.4, 55.6, 38.1, 27.9, 20.6, 20.5;
N-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyloxycarbonyl)-l-leucyl-O-
(tert-butyl)-l-serine tert-butyl ester (21): The general procedure for dipep-
tide coupling was used with: O-(tert-butyl)-l-serine-tert-butyl ester
(122 mg, 0.56 mmol), AGalOC-leucine 14 (228 mg, 0.45 mmol), 1-Hydroxy-
azabenzotriazole (HOAt) (96 mg, 0.71 mmol) in dry CH2Cl2 (40 mL), and
EDC (94 mg, 0.49 mmol) in dry CH2Cl2 (5 mL). The b-dipeptide 21
(235 mg, 74%) was isolated as a white foam. M.p. 79 ± 828C; Rf 0.40
(ethyl acetate/hexane 1:1); [a]D22 16.0 (c 1.0 in CHCl3); 1H NMR
(500 MHz, CDCl3): d 6.53 (d, J 8.1 Hz, 1H), 5.60 (d, J 8.4 Hz, 1H),
5.45 (d, J 8.3 Hz, 1H), 5.41 (d, J 3.2 Hz, 1H), 5.32 (dd, J 10.4, 8.4 Hz,
1H), 5.06 (dd, J 10.4, 3.4 Hz, 1H), 4.54 (dt, J 8.1, 2.8 Hz, 1H), 4.20 (m,
1H), 4.15 (d, J 6.7 Hz, 2H), 4.05 (t, J 7.2 Hz, 1H), 3.77 (dd, J 8.8,
2.8 Hz, 1H), 3.52 (dd, J 8.9, 2.9 Hz, 1H), 2.16 (s, 3H), 2.06 (s, 3H), 1.98 (s,
3H), 1.69 ± 1.64 (m, 2H), 1.58 ± 1.50 (m,1H), 1.45 (s, 9H), 1.15 (s, 9H), 0.96
(d, J 6.3 Hz, 3H), 0.94 (d, J 6.3 Hz, 3H); 13C NMR (125 MHz, CDCl3):
d 171.0, 170.3, 170.1, 170.0, 169.7, 169.0, 153.5, 93.4, 82.0, 73.2, 71.3, 70.9,
67.6, 66.8, 62.0, 60.8, 53.7, 53.2, 42.0, 28.0, 27.3, 24.6, 22.9, 21.8, 20.6, 20.5;
HRMS (FAB-3-NBA) [MH] : calcd 683.2663; found 683.2748.
N-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyloxycarbonyl)-l-leucyl-l-
serine benzyl ester (18):
HRMS (FAB-3-NBA) [MH] : calcd 705.3446; found 705.3424; elemental
The general procedure for dipeptide coupling was used with: l-serine-
benzyl ester´ TsOH (93 mg, 0.30 mmol), NEt3 (30 mg, 42 mL, 0.30 mmol),
AGalOC-leucine acid 14 (124 mg, 0.25 mmol) in dry CH2Cl2 (10 mL), and
EEDQ (93 mg, 0.38 mmol) in dry CH2Cl2 (2 mL). The b-dipeptide 18
(69 mg, 40%) was isolated as a colorless oil. Rf 0.30 (ethyl acetate/hexane
2:1); [a]D22 2.2 (c 1.35 in CHCl3); 1H NMR (250 MHz, CDCl3): d
7.28 (brs, 5H), 6.96 (d, J 7.9 Hz, 1H), 5.57 (d, J 8.2 Hz, 1H), 5.46 (d, J
7.9 Hz, 1H), 5.35 (d, J 3.2 Hz, 1H), 5.23 (t, J 8.3 Hz, 1H), 5.14 (s, 2H),
5.03 (dd, J 10.3, 3.3 Hz, 1H), 4.65 ± 4.61 (m, 1H), 4.22 ± 4.16 (m, 1H),
4.09 ± 3.99 (m, 3H), 3.94 (dd, J 11.5, 3.2 Hz, 1H), 3.83 (dd, J 11.3,
3.2 Hz, 1H), 2.80 (brs, 1H), 2.09 (s, 3H), 1.98 (s, 3H), 1.96 (s, 3H), 1.92 (s,
3H), 1.60 ± 1.39 (m, 3H), 0.85 (d, J 5.6 Hz, 6H); 13C NMR (125 MHz,
CDCl3): d 171.9, 170.3, 170.2, 170.1, 170.0, 169.9, 153.9, 135.1, 128.7, 128.6,
128.2, 128.1, 93.6, 71.4, 70.7, 67.8, 67.6, 66.8, 62.8, 60.4, 54.8, 53.7, 41.3, 24.6,
analysis calcd (%) for C32H52N2O15: C 54.54, H 7.44, N 3.97; found C 54.33,
H 7.48, N 3.81.
General procedure for lipase WG catalyzed cleavage of acetate groups to
give compounds 22 and 23
N-(b-d-galactopyranosyloxycarbonyl)-l-phenylalanyl-l-valine tert-butyl es-
ter (22): A solution of dipeptide 15 (55 mg, 0.08 mmol) in acetone (2.5 mL)
was added to a solution of lipase WG (40 mg, 3.2 Units, Fluka) in Na-
phosphate buffer (0.07m, 47.5 mL, pH 7.0). The reaction was incubated at
378C and stirred for 48 h. A saturated sodium chloride solution (50 mL)
was added, and the crude product was extracted into ethyl acetate (5 Â
25 mL). The combined organic phases were dried over MgSO4, filtered,
and concentrated under reduced pressure to give the pure, free galactose b-
dipeptide 22 (29 mg, 69%) as an amorphous white wax. Rf 0.26 (chloro-
form/methanol 9:1); [a]2D4 8.9 (c 0.47 in CHCl3); 1H NMR (500 MHz,
CD3OD): d 7.29 ± 7.18 (m, 5H), 5.22 (d, J 8.1 Hz, 1H), 4.50 (dd, J 9.0,
5.3 Hz, 1H), 4.19 (d, J 5.9 Hz, 1H), 3.85 (d, J 3.0 Hz, 1H), 3.71 ± 3.65
(m, 2H), 3.63 (dd, J 9.8, 8.1 Hz, 1H), 3.58 (t, J 6.0 Hz, 1H), 3.50 (dd,
J 9.7, 3.3 Hz, 1H), 3.31 (dd, J 14.0, 5.3 Hz, 1H), 2.88 (dd, J 14.0,
9.0 Hz, 1H), 2.13 (m, 1H), 1.47 (s, 9H), 0.95 (dd, J 6.8, 2.1 Hz, 6H);
13C NMR (125 MHz, CD3OD): d 173.9, 171.9, 156.8, 138.2, 130.3, 129.5,
127.8, 97.5, 82.8, 77.3, 74.7, 71.3, 69.9, 62.2, 59.8, 57.3, 39.0, 31.9, 28.3, 19.5,
22.9, 21.8, 20.7, 20.6, 20.5; HRMS (FAB-3-NBA) [MH] : calcd 683.2663;
found 683.2549.
N-(2,3,4,6-Tetra-O-acetyl-b-d-galactopyranosyloxycarbonyl)-l-leucyl-l-
alanine tert-butyl ester (19): The general procedure for dipeptide coupling
was used with: l-alanine-tert-butyl ester hydrochloride (62 mg, 0.34 mmol),
NEt3 (34 mg, 47 mL, 0.34 mmol); AGalOC-leucine acid 14 (156 mg,
0.31 mmol), EDC (73 mg, 0.37 mmol), and HOBt (72 mg, 0.47 mmol) were
added to the reaction flask. The reaction was cooled (08C) and then DMF
(10 mL) was added. After 14 h, the DMF was removed under reduced
pressure. The crude residue was dissolved in ethyl acetate, extracted, and
purified as described above. The b-dipeptide 19 (101 mg, 52%) was isolated
as a colorless oil. Rf 0.23 (ethyl acetate/hexane 1:1); [a]D22 1.3 (c 0.6
18.5; HRMS (FAB-3-NBA) [MNa] : calcd 549.2424; found 549.2402.
N-(b-d-Galactopyranosyloxycarbonyl)-l-phenylalanyl-l-alanine tert-butyl
ester (23): The general procedure for lipase WG catalyzed cleavage was
used with: lipase WG (110 mg, 8.8 Units, Fluka) in Na-phosphate buffer
(0.07m, 15 mL, pH 7.0), and dipeptide 16 (126 mg, 0.19 mmol) in acetone
(0.75 mL). The reaction was incubated at 378C and for 48 h. Pure, free
galactose b-dipeptide 23 (52 mg, 55%) was isolated as a white wax. Rf
0.40 (methanol/ethyl acetate 1:4); [a]D22 À10.1 (c 1.0 in CH3OH);
1H NMR (250 MHz, CD3OD): d 7.30 ± 7.19 (m, 5H), 5.21 (d, J 8.0 Hz,
1H), 4.41 (dd, J 9.3, 4.8 Hz, 1H), 4.27 (q, J 7.2 Hz, 1H), 3.83 (d, J
3.0 Hz, 1H), 3.68 ± 3.47 (m, 5H), 3.15 (dd, J 14.0, 4.8 Hz, 1H), 2.86 (dd,
J 14.0, 9.3 Hz, 1H), 1.46 (s, 9H), 1.35 (d, J 7.2 Hz, 3H); 13C NMR
(100 MHz, CD3OD): d 173.6, 173.2, 156.8, 138.3, 130.4, 129.5, 127.8, 97.5,
1
in CHCl3); H NMR (400 MHz, CDCl3): d 6.44 (d, J 7.3 Hz, 1H), 5.63
(d, J 8.4 Hz, 1H), 5.41 (d, J 3.2 Hz, 1H), 5.36 (d, J 8.4 Hz, 1H), 5.30
(dd, J 10.4, 8.3 Hz, 1H), 5.07 (dd, J 10.3, 3.4 Hz, 1H), 4.40 (q, J 7.1 Hz,
1H), 4.19 ± 4.04 (m, 4H), 2.15 (s, 3H), 2.06 (s, 3H), 2.03 (s, 3H), 1.98 (s, 3H),
1.69 ± 1.48 (m, 3H), 1.45 (s, 9H), 1.35 (d, J 7.1 Hz, 3H), 0.93 (d, J 6.2 Hz,
6H); 13C NMR (100 MHz, CDCl3): d 171.8, 170.8, 170.3, 170.2, 170.0,
169.7, 153.6, 93.5, 82.2, 71.4, 70.9, 67.7, 66.8, 60.9, 53.6, 48.7, 41.7, 27.9, 24.6,
22.9, 21.8, 20.7, 20.6, 18.5; HRMS (FAB-3-NBA) [MH] : calcd 633.2871;
found 633.2938.
Chem. Eur. J. 2000, 6, No. 20
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0620-3719 $ 17.50+.50/0
3719