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Chapter 3
group), 7.19 (d, 4H, J(H,H) = 7.2 Hz, CH aromatic tosyl group), 6.52 (bs, 2H, N η -H arginine
side chain), 3.67-3.60 (m, 4H, CH 3 methyl ester + C(2)Hα), 3.18-3.00 (m, 3H, ψ CH 2 +
C(5)Hα), 2.74-2.64 (m, 4H, CH 2 arginine side chain), 2.36 (s, 6H, CH 3 tosyl group), 1.54-
1.45 (m, 8H, CH 2 arginine side chain), 1.37 (s, 9H, CH 3 Boc group). 13 C-NMR (75 MHz,
CDCl 3 , some signals are missing due to the pseudoequivalence of the arginine side chains):
δ(ppm) 174.3, 156.9, 156.6, 142.0, 140.6, 129.2, 125.9, 79.7, 60.8, 52.3, 52.1, 50.4, 40.7,
29.8, 28.3, 25.4, 21.4. ESI-MS (CH 3 OH, positive ions): calculated m/z: 739.3 (MH + ), 761.3
(MNa + ), 777.3 (MK + ), found: 739.7, 761.7, 777.7. HRMS (ESI + ): calcd m/z for C 32 H 51 N 8 O 8 S 2
(MH + ): 739.3271, found: 739.3272.
N α -Boc-[L-Argψ-(N ω -Tosyl)-D-Arg-((N ω -Tosyl)]-OH. N α -Boc-[L-Argψ-(N ω -Tosyl)-D-
Arg-((N ω -Tosyl)] methyl ester (0.3g, 0.4 mmol) was dissolved in THF:H 2 O = 1:1 (10ml).
NaOH (0.16g, 4mmol) was added and the mixture was stirred at room temperature for 1 hour
and 30 min. THF was evaporated and the product was precipitated as a white solid at pH= 6.5,
filtered and dried under vacuum. Yield: 87%. 1 H-NMR (300MHz , CD 3 OD): δ(ppm) 7.72 (d,
4H, J(H,H)= 6 Hz, CH aromatic tosyl group), 7.27 (d, 4H, J(H,H) = 8 Hz, CH aromatic tosyl
group), 3.59-3.55 (m, 1H, C(2)-H α), 3.30-3.29 (m, 2H ψ CH 2 ) 3.16-3.12 (m, 4H CH 2
ariginine side chain), 2.93-2.86 (m, 3H, C(5)Hα), 2.36 (s, 6H, CH 3 tosyl group), 1.89-1.82
(m, 4H, CH 2 ariginine side chain), 1.64-1.51 (m, 4H CH 2 side chain ariginine) 1.43 (s, 9H,
CH 3 Boc group). 13 C-NMR ( 75 MHz, CDCl 3 , some signals are missing due to the
pseudoequivalence of the arginine side chains): δ (ppm) 173.5, 159.2, 159.0, 143.9, 142.4,
130.6, 127.4, 81.3, 63.8 , 53.4, 50.2, 41.5, 31.2, 28.8, 26.9, 21.8. ESI-MS (CH 3 OH, positive
ions): calculated m/z: 747.3 (MNa + ), 763.3 (MK + ), found: 747.5, 763.2. HRMS (ESI + ): calcd
m/z for C 31 H 49 N 8 O 8 S 2 (MH + ): 725.3115, found: 725.3117.
N α -Boc-[L-Argψ-(N ω -Tosyl)-D-Arg-(N α -Fmoc)-(N ω -Tosyl)]-OH.
Bis(trimethylsilyl)acetamide (BTSA) (0.21ml, 0.86 mmol) and DIPEA ( 0.05ml, 0.29 mmol)
were added to N α -Boc-[L-Argψ-(N ω -Tosyl)-D-Arg-(N ω -Tosyl)]-OH (0.21g, 0.29 mmol)
suspended in DCM (15 ml), with exclusion of humidity by a CaCl 2 drying tube. When the
solution was nearly clear (10-15 min were usually required), Fmoc-Cl (0.1g, 0.58 mmol) was
added and the mixture was stirred for 2 hours at room temperature. Methanol (1 ml ) was
carefully added and the mixture was stirred for an additional 15 min, diluted with 15 ml of
DCM, washed with 1M potassium hydrogen sulphate (3 times) and brine (times), dried over
magnesium sulfate and evaporated to dryness. The residue was purified by flash
chromatography (dichlomethane:methanol = 9:1) and the product was obtained as a white
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