under vacuum and the residue puriÐed by Ñash chromatog-
raphy (eluent; methanol (10%) in ethyl acetate) to yield an
opaque solid which was dried under high vacuum. Yield: 5.47
g, 4.77 mmol, 90%. 1H NMR (CD OD/CDCl 1 : 1) dH (270
the residue dried in a vacuum oven yielding a very thick
honey coloured oil. TLC (methanol (5%) in ethyl acetate) fol-
lowed by development with iodine and ninhydrin indicated
the presence of only one compound and that it contained a
primary amine function. Yield: 6.085 g, 9.67 mmol, 73%. 1H
NMR (CDCl ) dH (270 MHz); 1.43 (18H, s, CHCH ), 1.47
3
3
MHz); 1.26 (12H, t, CHCH ), 1.29 (12H, t, CH CH ), 1.92È
3
2
3
2.51 (30H, m, CHCH CH and NH ), 4.13 (8H, q, CH CH ),
2
2
2
2
3
3
3
4.20 (8H, q, CH CH ), 4.24È4.40 (3H, m, CHCH CH ), 4.54
(4H, m, CHCH CH ), 8.10 (1H, d, NH), 8.23 (1H, d, NH), 8.53
(18H, s, CH CH ), 1.78È2.37 (14H, m, CHCH CH and NH ),
2
3
2
2
2
3
2
2
2
4.58 (3H, m, CHCH CH ), 8.16 (1H, d, NH); 13C NMR
2
2
2
2
(1H, d, NH), 8.73 (1H, d, NH), 9.01 (1H, d, NH); 13C NMR
(CD OD) dC; 27.68 (b CH , r or r ), 27.91 (b CH , r or r ),
3
2
1
2
2
1
2
(CD OD) dC; 14.45 (c CH CH ), 14.50 (a CH CH ), 27.23 (b
28.31 (c CH ), 28.40 (a CH ), 32.42 (c CH , r or r ), 32.52 (c
3
2
3
2
3
3 3 2 1 2
CH , r or r ), 32.65 (b CH , r ), 33.01 (c CH , r ), 53.48 (a
or c CH ), 27.39 (b or c CH ), 27.52 (b or c CH ), 28.18 (b or
2
2
2
2 1 2 2 3 2 3
CH, r or r ), 53.66 (a CH, r or r ), 54.96 (a CH, r ), 81.68 (c
c CH ), 28.56 (b or c CH ), 30.86 (b or c CH ), 31.04 (b or c
2
2
2
1
2
1
2
3
CH ), 31.14 (b or c CH ), 32.24 (b or c CH ), 32.36 (b or c
CH ), 32.42 (b or c CH ), 52.73 (a CH), 52.80 (a CH), 52.83 (a
C(CH ) , r /r ), 83.47 (a C(CH ) , r or r ), 83.65 (a C(CH ) ,
2
2
2
2
3 3 1 2
3 3
1
2
3 3
r
or r ), 173.10 (CO), 173.14 (CO), 173.44 (CO), 173.63 (CO),
2
1
2
CH), 53.21 (a CH), 53.47 (a CH), 53.90 (a CH), 61.45 (c
CH CH ), 61.49 (c CH CH ), 62.51 (a CH CH ), 62.54 (a
175.19 (CO), 176.78 (CO); FAB-MS found MH` 630 and
[M ] Na]` 652; C
H
N O requires 629.39.
2
2
3
3
2
3
2
3
31 55
3
10
CH CH ), 172.92 (CO), 173.00 (CO), 173.13 (CO), 173.40
(CO), 173.44 (CO), 173.68 (CO), 173.73 (CO), 173.76 (CO),
174.22 (CO), 174.33 (CO), 174.44 (CO), 174.82 (CO); FAB-MS
[G0.5]-CBZ-L-Glutamic acid di-L-phenylalanine ethyl ester
(7). A solution containing L-phenylalanine ethyl ester hydro-
chloride (25 g, 109 mmol) and triethylamine (8.8 ml, 12.1 g,
120 mmol) dissolved in DCM (150 ml) was prepared and
cooled over ice. A second solution containing CBZ-L-glutamic
acid (14.56 g, 51.8 mmol), HBTU (45.51 g, 120 mmol), HOBt
(18.36 g, 120 mmol) and DIPEA (31 g, 240 mmol) in DCM
(200 ml) was made at 0 ¡C and stirred for 20 min. The Ðrst
solution was added to the second and the reaction mixture
was stirred for 45 min at 0 ¡C. The reaction mixture was
allowed to warm to room temperature whilst stirring for a
further 6 h and placed in a refrigerator overnight. The volume
of the solvent was reduced to approximately 100 ml under
vacuum and then transferred to a beaker and HCl (5% soln.,
50 ml) was added. The solid was collected by Ðltration and
washed with DCM. The Ðltrate and the washings were com-
bined and washed with water (3 ] 40 ml), HCl (5% solution,
found MH` 1146 and [M ] Na]` 1168; C
requires 1145.56.
H
N O
51 83
7
22
[G1]-CBZ-L-Glutamic acid tert-butyl ester (5). A solution
containing L-glutamic acid di-tert-butyl ester hydrochloride (5
g, 16.9 mmol) and DIPEA (2.94 ml, 2.18 g, 16.9 mmol) dis-
solved in DCM (50 ml, dist.) was prepared and cooled over
ice. A second solution containing CBZ-L-glutamic acid (2.27 g,
8.05 mmol), HBTU (7.33 g, 19.32 mmol), HOBt (2.96 g, 19.32
mmol) and DIPEA (6.7 ml, 5.0 g, 38.7 mmol) in DCM (70 ml)
was made at 0 ¡C and stirred for 20 min. The Ðrst solution was
added to the second and the reaction mixture was stirred for
45 min at 0 ¡C. The reaction mixture was allowed to warm to
room temperature whilst stirring for a further 3 h. The volume
of the solvent was reduced to approximately 50 ml under
vacuum and water was added. The DCM layer was washed
with water (3 ] 40 ml), HCl (5% solution, 3 ] 40 ml), water
3 ] 40 ml), water (2 ] 30 ml), NaHCO (sat. soln., 3 ] 40 ml),
3
water (2 ] 30 ml) and brine (50 ml). The DCM was removed
(2 ] 30 ml), NaHCO (sat. soln., 3 ] 40 ml), water (2 ] 30 ml)
under vacuum and the residue redissolved in methanol. The
product was puriÐed by trituration from methanol upon the
addition of water. The precipitate was collected by Ðltration,
washed with water and then partitioned between DCM and
water. The DCM was collected and washed with brine (sat
soln., 30 ml). This crude product was puriÐed by Ñash chro-
matography (eluent: ethyl acetate) to yield a opaque solid.
TLC (eluent: ethyl acetate) indicated the presence of only one
compound. Yield: 29.29 g, 46.1 mmol, 90%. Elemental
3
and brine (sat. soln., 50 ml). The DCM was removed under
vacuum and the residue was puriÐed by Ñash chromatography
(eluent: hexane : ethyl acetate 1 : 1). TLC (eluent: methanol
(5%) in ethyl acetate) indicated the presence of only one com-
pound. Yield: 5.25 g, 6.88 mmol, 86%. 1H NMR (CDCl ) dH
3
(270 MHz); 1.43 (18H, s, CHCH ), 1.47 (18H, s, CH CH ),
3
2
3
1.79È2.38 (12H, m, CHCH CH ), 4.07 (1H, m, CHCH CH ),
4.58 (2H, m, CHCH CH ), 5.07 (2H, d, CH Ar), 5.53 (1H, d,
ArCH CO NH), 7.31 (5H, s, Ar), 7.83 (1H, d, NH), 8.16 (1H,
d, NH); 13C NMR (CDCl ) dC; 26.60 (b CH , r or r ), 26.83
(b CH , r or r ), 27.80 (c CH ), 27.88 (a CH ), 29.13 (b CH ,
r ), 31.34 (c CH , r or r ), 31.59 (c CH , r or r ), 31.85 (c
CH , r ), 51.93 (a CH, r or r ), 52.16 (a CH, r or r ), 53.29 (a
CH, r ), 66.51 (Ar-CH ), 80.36 (c C(CH ) , r or r ), 80.46 (c
3 3
C(CH ) , r or r ), 82.83 (a C(CH ) , r or r ), 82.93 (a
3 3 3 3
C(CH ) , r or r ), 127.79 (p-ArC), 128.23 (o/m-ArC), 136.17
(ipso-ArC), 155.10 (Ar-CH -O-CO), 171.46 (CO), 171.56 (CO),
171.69 (CO), 172.52 (CO), 173.09 (CO), 173.33 (CO); FAB-MS
2
2
2
2
2
2
2
analysis found C: 66.5, H: 6.5, N: 6.7, C
H
N O requires
2
2
35 41
3
8
C: 66.6, H: 6.5, N: 6.7%. 1H NMR (CDCl ) dH (270 MHz);
3
2
1
2
3
1.17È1.28 (6H, m, CHCH ), 1.75È2.28 (4H, m, CHCH CH ),
2
1
2
3
3
2
3
2
3
2
2.80È3.12 (4H, m, CHCH -Ar), 4.14 (5H, m, CH CH and
3
2
1
2
2
1
2
2
2
CHCH CH ), 4.84 (2H, q, CHCH Ar), 5.04 (2H, d,
2
3
1
2
1
2
2
2
2
ArCH CO ), 5.57 (1H, d, ArCH CO NH), 7.14È7.30 (15H, m,
3
2
1
2
2
2
2
2
ArH), 7.33 (1H, d, NH), 7.90 (1H, d, NH); 13C NMR (CDCl )
1
1
2
2
1
2
3
dC; 13.86 (CH CH ), 13.92 (CH CH ), 29.10 (b CH , r ),
3 3
2
3
2
1
3
2
2
3
31.72 (c CH , r ), 37.19 (b CH , r or r ), 37.50 (b CH , r or
2
2
3
2
2
1
r ), 53.21 (a CH, r ), 53.57 (a CH, r /r ), 61.61 (CH CH ),
1 2
61.75 (CH CH ), 66.53 (Ar-CH -O-), 126.80 (p-ArC), 127.76
(p-ArC), 128.24 (o-ArC), 128.32 (o-ArC), 128.99 (m-ArC),
129.09 (m-ArC), 135.86 (ipso-ArC), 136.08 (ipso-ArC), 136.23
2
3
2
3
found MH` 764 and [M ] Na]` 1786;
requires 763.43.
C
H
N O
39 61
3
12
2
3
2
[G1]-NH -L-Glutamic acid tert-butyl ester (6). [G1]-CBZ-
(ipso-ArC), 155.21 (Ar-CH -O-CO), 171.51 (CO), 172.32 (CO),
173.01 (CO), 173.20 (CO); FAB-MS found MH` 632 and
2
2
L-Glutamic acid tert-butyl ester (10.12 g, 13.32 mmol) and
ammonium formate (3.4 g, 54 mmol) were dissolved in meth-
anol (100 ml) containing DCM (15 ml). A 5% palladium on
carbon catalyst (1 g) was added and the solution was sonicat-
ed for 3 h under a hydrogen atmosphere. The carbon was
Ðltered o† and the Ðltrate evaporated to dryness under
vacuum. The residue was partitioned between DCM (100 ml)
and water (50 ml). The DCM layer was washed with water
(2 ] 40 ml), HCl (5% solution, 2 ] 40 ml), water (2 ] 30 ml),
[M ] Na]` 654; C
H
N O requires 631.29.
35 41
3 8
[G0.5]-NH -L-Glutamic acid di-L-phenylalanine ethyl ester
2
(8). [G0.5]-CBZ-L-Glutamic acid di-L-phenylalanine ethyl
ester (28.12 g, 44.5 mmol, compound 7) and ammonium
formate (11.7 g, 186 mmol) were dissolved in methanol (150
ml) containing DCM (10 ml). A 5% palladium on carbon
catalyst (3 g) was added and the solution was stirred for 6 h at
room temperature. The carbon was removed by Ðltration and
washed with methanol. The Ðltrate was combined with the
NaHCO (sat. soln., 3 ] 40 ml), water (2 ] 30 ml) and brine
3
(sat. soln., 50 ml). The DCM was removed under vacuum and
816
New J. Chem., 2001, 25, 807È818