1665, 1495 and 1454; δH(400 MHz; CDCl3) 1.40 (9H, s, t-Bu),
1.80–1.95 (6H, m), 2.24–2.54 (10H, m), 2.70–2.78 (2H, m),
3.86–3.87 (1H, m, HCNH), 4.12–4.13 (1H, m, HCNH), 4.20–
4.30 (1H, m, HCNH), νA = 4.78, νB = 4.71 (2H, AB, JAB 12.0,
OCH2CCl3), 5.06–5.14 (6H, m, H2CPh), 5.35 [1H, d, J 8.2,
O(CO)NH], 6.54 [1H, d, J 7.5, C(CO)NH], 6.79 [1H, d, J 7.4,
C(CO)NH] and 7.31–7.38 (15H, m, arom. H); δC(100 MHz;
CDCl3) 28.3, 28.7, 28.9, 29.7, 31.0, 31.1, 38.6, 40.5, 41.0, 46.0,
46.6, 47.7, 66.3, 66.4, 66.6, 74.0, 77.2, 79.3, 94.7, 128.2 (2C),
128.3 (2C), 128.4, 128.5, 128.6 (2C), 135.7, 135.8, 135.9, 155.7,
169.7, 170.6, 173.0 and 173.1; m/z (FAB) 1921.4 [6.2%, (2M ϩ
Na)ϩ], 1899.4 [22.0, (2M ϩ 1)ϩ], 972.2 [13.5, (M ϩ Na)ϩ], 950.2
[33.3, (M ϩ 1)ϩ] and 850.1 [100, (M Ϫ Boc)ϩ].
m), 2.75 (3H, d, J 6.6), 3.56–3.63 (2H, m), 4.07–4.12 (1H, m,
HCNH), 4.45–4.54 (4H, m), 4.64–4.71 (2H, m, OCH2CCl3),
5.07–5.12 (2H, m), 5.13–5.19 (2H, m), 5.87 [1H, d, J 8.2,
O(CO)NH], 6.33 [1H, d, J 8.1, C(CO)NH], 6.65 [1H, d, J 7.6,
C(CO)NH] and 7.26–7.37 (15H, m, arom. H); δC(100 MHz;
CDCl3) 28.3, 28.5, 31.1, 35.8, 37.7, 40.1, 45.9, 46.5, 50.6, 66.5,
67.3, 70.6, 73.4, 74.1, 77.2, 79.9, 94.7, 128.0, 128.1, 128.2, 128.3,
128.5, 128.6, 135.5, 135.8, 137.4, 155.7, 169.6, 169.9, 170.2,
171.7 and 173.1; m/z (FAB) 1759.4 [3.2%, (2M ϩ 1)ϩ], 880.2
[43.3, (M ϩ 1)ϩ] and 780.2 [100, (M Ϫ Boc)ϩ].
Boc-N-[-â-D-Asp(á-OBn)-â-HGlu(OBn)-â-HSer(OBn)]2-
OCH2CCl3 19. Peptide 18 (500 mg, 0.57 mmol) was deprotected
in 90% (v/v) HOAc (24 ml) with zinc powder (4 g) according to
general procedure F. A further portion of peptide 18 (501 mg,
0.57 mmol) was deprotected according to general procedure C.
The fragments were coupled according to general procedure D
with Et3N (0.4 ml, 2.85 mmol), HOBt (85 mg, 0.63 mmol) and
EDC (120 mg, 0.63 mmol). FC [CHCl3–7% (v/v) MeOH] gave
compound 19 (472 mg, 55%) as an amorphous solid, mp 166–
176 ЊC (decomp.); [α]Dr.t. Ϫ12.2 (c 0.93, CHCl3); νmax(CHCl3)/cmϪ1
3426, 1733, 1667, 1498 and 1455; δH(400 MHz; CDCl3) 1.38
(9H, s, t-Bu), 1.75–1.88 (4H, m), 2.20–2.56 (12H, m), 2.64–2.82
(4H, m), 3.48–3.63 (4H, m), 4.10–4.15 (2H, m, HCNH), 4.40–
4.73 (10H, m), 5.06–5.17 (8H, m), 5.93 (1H, d, J 8.4, NH), 6.31
(1H, d, J 8.7, NH), 6.89 (1H, d, J 8.4, NH), 6.94 (1H, d, J 8.4,
NH) and 7.2–7.38 (30 H, m, arom. H); δC(100 MHz; CDCl3)
23.0, 28.3, 28.5, 28.8, 31.1, 35.8, 37.1, 37.3, 37.6, 40.0, 40.3,
45.9, 45.9, 46.3, 46.4, 46.5, 46.7, 49.0, 49.6, 50.6, 66.4, 66.5,
67.2, 67.4, 67.5, 70.6, 71.1, 73.2, 73.4, 74.1, 77.2, 79.8, 94.7,
127.66, 127.86, 127.95, 128.00, 128.02, 128.08, 128.10, 128.15,
128.21, 128.23, 128.30, 128.36, 128.39, 128.42, 128.48, 128.56,
128.58, 128.60, 128.62, 135.36, 135.44, 135.6, 135.8, 135.9,
137.37, 137.43, 137.9, 169.7, 169.8, 169.9, 170.0, 170.2, 170.3,
170.5, 171.25, 171.34, 171.8, 172.9, 173.0 and 173.3; m/z (FAB)
1531.5 [20.8%, (M ϩ Na)ϩ], 1509.5 [28.4, (M ϩ 1)ϩ] and 1409.4
[100, (M Ϫ Boc)ϩ].
Boc-N-[â-HGlu(OBn)]6-OCH2CCl3 16. Peptide 15 (1.5 g, 1.6
mmol) was deprotected in 90% (v/v) HOAc (66 ml) with zinc
powder (10 g) according to general procedure F. A further por-
tion of peptide 15 (1.5 g, 1.6 mmol) was deprotected according
to general procedure C. Both fragments were dissolved in
CH2Cl2 (30 ml), Et3N (1.1 ml, 7.9 mmol), HOBt (235 mg, 1.7
mmol) and EDC (333 mg, 1.7 mmol) were added, and the mix-
ture was stirred overnight at rt. The resulting yellow mixture
was diluted with CHCl3 and washed successively with 1 aq.
NaHSO4 and saturated aq. NaHCO3. The organic phase was
washed with aq. NaCl, dried (MgSO4) and concentrated.
Recrystallisation (toluene, 60 ЊC) gave compound 16 (1.86 g,
72%) as a glass, mp 199–201 ЊC (decomp.); [α]Dr.t. Ϫ14.7 (c 0.88,
CHCl3); νmax(CHCl3)/cmϪ1 3366, 1731, 1661 and 1498; δH(400
MHz; CDCl3) 1.40 (9H, s, t-Bu), 1.60–2.00 (12H, m), 2.17–2.41
(24H, m), 3.80–3.91 (1H, m, HCNH), 4.00–4.15 (3H, m,
HCNH), 4.20–4.40 (2H, m, HCNH), νA = 4.76, νB = 4.70 (2H,
AB, JAB 12.0, OCH2CCl3), 5.07–5.10 (12H, m, H2CPh), 5.48
[1H, m, O(CO)NH], 6.64–7.02 [5H, m, C(CO)NH] and 7.29–
7.35 (30H, m, arom. H); m/z (FAB) 1671.5 [13.6%, (M ϩ Na)ϩ],
1649.6 [21.1, (M ϩ 1)ϩ] and 1549.5 [100, (M Ϫ Boc)ϩ].
Boc-N-â-HGlu(OBn)-â-HSer(OBn)-OCH2CCl3 17. Com-
pound 8 (958 mg, 2.17 mmol) was deprotected according to
general procedure C. The resulting aminoester and compound 5
(763 mg, 2.17 mmol), Et3N (1.51 ml, 10.85 mmol), HOBt (323
mg, 2.38 mmol) and EDC (458 mg, 2.38 mmol) were trans-
formed according to general procedure D. FC (ethyl acetate–
pentane 2:3) yielded compound 17 (942 mg, 64%) as an
amorphous solid, mp 108–109 ЊC; [α]Dr.t. Ϫ5.4 (c 1.07, CHCl3)
(Found: C, 55.3; H, 5.9; N, 4.3. C31H39Cl3N2O8 requires C, 55.2;
H, 5.8; N, 4.16%); νmax(CHCl3)/cmϪ1 3648, 3430, 1704 and 1497;
δH(400 MHz; CDCl3) 1.41 (9H, s, t-Bu), 1.82–1.94 (2H, m),
2.31–2.43 (4H, m), 2.77 (2H, d, J 6.2), 3.52–3.63 (2H, m), 3.83–
3.91 (1H, m, HCNH), 4.45–4.54 (3H, m), νA = 4.67, νB = 4.64
(2H, AB, JAB 12.0, OCH2CCl3), 5.07–5.14 (2H, m), 5.32 [1H, d,
J 7.9, O(CO)NH], 6.33 [1H, d, J 8.1, C(CO)NH] and 7.31–7.38
(10H, m, arom. H); δC(100 MHz; CDCl3) 28.4, 29.5, 31.1, 35.8,
41.0, 45.9, 47.8, 49.2, 66.4, 70.5, 73.4, 74.1, 79.4, 94.8, 127.9,
128.0, 128.2, 128.3, 128.4, 128.5, 128.6, 135.9, 137.5, 155.6,
169.7, 170.2 and 173.1; m/z (FAB) 1345.5 [8.3%, (2M ϩ 1)ϩ],
673.2 [77.5, (M ϩ 1)ϩ] and 573.2 [100, (M Ϫ Boc)ϩ].
H2N-N-[-â-D-Asp(á-OBn)-â-HGlu(OBn)-â-HSer(OBn)]2-OH
20. Peptide 19 (144 mg, 0.095 mmol) was deprotected in 90%
(v/v) HOAc (3.3 ml) with zinc powder (500 mg) according to
general procedure F. The supension was filtered and the residue
was taken up in CHCl3 and washed successively with 1 aq.
HCl and brine. The organic layer was dried (MgSO4) and
evaporated. The resulting peptide was deprotected according to
general procedure C. Purification by preparative RP-HPLC
[A: water (0.1% TFA); B: CH3CN; 10 min 60% B, 10 to 15 min
80% B, 15 to 20 min 99% B] yielded compound 20 (66 mg, 55%)
as a glass, mp 148–150 ЊC; δH(500 MHz; CDCl3) see Tables 1
and 2.
cyclo[-â-D-Asp(á-OBn)-â-D-Asp(á-OBn)-â-D-Asp(á-OBn)-]
21. Peptide 12 (1.73 g, 2 mmol) was deprotected in 90% (v/v)
HOAc (60 ml) with zinc powder (5.5 g) according to general
procedure F. The resulting peptide was transformed according
to general procedure E with pentafluorophenol (387 mg, 2.1
mmol) and EDC (402 mg, 2.1 mmol) in CH2Cl2. The resulting
ester was deprotected according to general procedure C in
CH2Cl2 (80 ml) and TFA (20 ml). The resulting peptide was
transformed according to general procedure E and the precipi-
tate was collected by filtration to give compound 21 (886 mg,
72%) as a powder, mp >300 ЊC (Found: C, 64.4; H, 5.7; N, 6.8.
C33H33N3O9 requires C, 64.4; H, 5.7; N, 6.8%); νmax(KBr)/cmϪ1
3288, 1740, 1674, 1560 and 1445; δH(400 MHz; CDCl3–TFA)
2.89 (3H, dd, J1 10.0, J2 14.4), 3.14 (3H, dd, J1 5.1, J2 14.4),
4.77 (3H, br s, HCNH), νA = 5.24, νB = 5.19 (6H, AB, JAB 12.0,
H2CPh), 7.26–7.37 (15H, m, arom. H) and 7.58 (3H, d, J 7.6,
NH) and 7.37–7.26 (15H, m, arom. H); δC(100 MHz; CDCl3–
TFA) 37.3, 50.6, 69.1, 133.9, 170.1 and 171.5; m/z (FAB) 638.2
[96.3%, (M ϩ Na)ϩ] and 616.3 [100, (M ϩ 1)ϩ].
Boc-N-â-D-Asp(á-OBn)-â-HGlu(OBn)-â-HSer(OBn)-OCH2-
CCl3 18. Compound 17 (3.47 g, 5.15 mmol) was deprotected
according to general procedure C. The resulting aminoester and
Boc-N--Asp(α-OBn)-CO2H (1.66 g, 5.15 mmol), Et3N (3.6 ml,
25.7 mmol), HOBt (765 mg, 5.66 mmol) and EDC (1.09 g, 5.66
mmol) were transformed according to general procedure D.
FC (ethyl acetate–pentane 2:3) with subsequent recrystallis-
ation from ethyl acetate–pentane yielded compound 18 (1.39 g,
31%) as an amorphous solid, mp 120–122 ЊC; [α]Dr.t. Ϫ10.1 (c
0.75, CHCl3) (Found: C, 57.4; H, 5.7; N, 4.8. C42H50Cl3N3O11
requires C, 57.4; H, 5.7; N, 4.8%); νmax(CHCl3)/cmϪ1 3430, 1711,
1667, 1498, 1454 and 1368; δH(400 MHz; CDCl3) 1.40 (9H, s,
t-Bu), 1.83–1.86 (2H, m), 2.21–2.41 (4H, m), 2.43–2.54 (1H,
3338
J. Chem. Soc., Perkin Trans. 1, 1998, 3331–3340