450
T. Aboul-Fadl, G. Rajeev and A. D. Broom
Vol 45
(2.11g, 25.125 mmol) in water (50 ml), solution of aliquat 336
(10.65 g, 26.35 mmol) and allyl bromide (2.37 ml, 27.45 mmol)
in DCM (100 ml) was added. The mixture was stirred vigorously
for 3 days at ambient temperature. The aqueous layer was then
separated and extracted three times with DCM (each of 100 ml).
The pooled organic layers were dried over anhydrous Na2SO4
and the solvent was evaporated under reduced pressure. The
residue was purified by flash chromatography (Pet. ether/EtOAc,
3:1) to give 10.3g (96%) of the title compound. 1HNMR
(CDCl3): 1.43(s, 9H), 1.45-1.66(bm, 4H), 1.73-1.89(bm, 2H),
3.07-3.26(bm, 2H), 4.24-4.35(m, 1H), 4.70-4.55(m, 2H), 5.09 (s,
2H), 5.21-5.38 (m, 3H), 5.75-6.03 (m, 1H), 7.33(bs, 5H). EIMS:
m/z = 421.3 [M+1]
in methanol (100 ml) and treated with Dowex®50Wx8.200 resin
(H+ form) for 10 minutes. The resin was filtered, washed with
methanol (20 ml) and the filtrate was evaporated under reduced
pressure to dryness to give 1.2 g (98%) of the title compound.
1HNMR (DMSO-d6): 1.25-1.55 (m, 12H), 1.92-2.04 (m, 2H),
3.03-3.43 (m, 6H), 3.53-3.99(m, 4H), 4.07-4.15 (t, 1H), 5.09 (s,
2H), 5.29-5.94 (m, 2H), 7.33-7.38 (m, 5H), 7.95 (s, 1H), 8.25 (s,
1H). EIMS: m/z = 630.31 (M+1); HRMS (FAB): 630.27099
(calcd), 630.27052 (found).
General procedures for synthesis of Nα-(aminoethyl)-Nα-
(1-methyl-6-mercaptopurin-9-methylcarbonyl)-L-lysine
polymers, (20). BOC-BHA-PEG-PS resin (60 mg, 0.12 mmol/g,
0.0036 meq.) was soaked in DCM (5 ml) for overnight then
stirred with 50% TFA in DCM (5 ml) for 30 minutes. The resin
was filtered, then washed with the following: DCM (2 ml), 10%
DIEA in DCM (1 ml) and dry DCM (2 ml). The resin was
suspended in dry DCM (5 ml) containing 10% CCl4 and stirred
gently with 16 (20 mg, 0.0317 mol), Ph3P (40 mg, 0.1525 mol),
and DIEA (40 µl, 0.1148 mol) for 45 minutes under an argon
atmosphere at ambient temperature. The resin was filtered,
washed with DCM (2 ml), suspended in DCM (1 ml) containing
10% Ac2O (1 ml) and 10% DIEA in DCM with shaking for 5
minutes, then filtered and washed with DCM. The resin was
stirred with 50% TFA in DCM (5 ml) for 30 minutes followed
by washing and repeating the previous steps for 3 cycles (trimer)
and 12 cycles (dodecamer). The resin was then treated with
HF/pyridine mixture containing 5% m-cresol (0.5 ml) for 5
hours at ambient temperature, filtered and the solvent removed
by lyophilization. The lyophilized product was purified by
HPLC using RP-C18 column for trimer PNA and RP-C8 column
for dodecamer PNA and gradient elution system consisting of
solvent (A), 0.1% TFA/water, and system (B), 0.1% TFA/ACN.
The percent of B is varied from 20% over a period 30 minutes
for 3-mer and 60% over a period of 20 minutes for 12-mer.
HPLC fractions of the targets were lyophilized to obtain the
products as yellowish white fluffy powder.
Nα-(2-Boc-Aminoethyl)-Nε-CBZ-L-lysine allyl ester (13).
Compound 11 (8.25 g, 19.27 mmol) was stirred with 50% TFA
(100 ml) in DCM for 20 minutes. The solvent was evaporated
under reduced pressure. To the solution of the residue in dry
methanol (100 ml), a solution of Boc-aminoacetaldehyde (3.45
g, 21.6 mmol) in dry methanol (25 ml) was added and the
mixture stirred for 15 minutes. NaBH3CN (1.38 g, 22 mmol)
was then added and the mixture stirred for 24 hours at ambient
temperature. Subsequently, water (30 ml) was added followed
by 10% solution of NaHSO4 in water (10 ml). Methanol was
evaporated and the aqueous residue was extracted with DCM
(3x75 ml), the combined organic layer was dried (Na2SO4),
filtered and evaporated under reduced pressure. The residue was
purified by flash chromatography (5% MeOH in DCM) to give
1
7.1 g (80%) of the titled compound. HNMR (CDCl3): 1.44(s,
9H), 1.46-1.60(m, 4H), 1.75-1.93(m, 2H), 3.14-3.22(m, 2H),
3.27-3.29(m, 2H) 4.24-4.35(m, 1H), 4.70-4.55(m, 2H), 5.09 (s,
2H), 5.26-5.37 (m, 4H), 5.75-6.03 (m, 1H), 7.26-7.38 (m, 5H).
EIMS: m/z = 464.35 (M+1); HRMS (FAB): 464.27606 (calcd),
464.27627 (found)
Allyl Nα-(2-Boc-Aminoethyl), Nα-(1-methyl-6-mercapto-
purin-9-methylcarbonyl)-Nε-CBZ-L-lysinate (15). Compounds
6 (2.24 g, 10 mmol) and 13 (4.64 g, 10 mmol) were dissolved
with stirring in anhydrous pyridine (50 ml) containing 10% CCl4
under an argon atmosphere at ambient temperature. Ph3P (5.06
g, 19.28 mmol) was added to the reaction mixture and the
stirring continued for 4 hours. Pyridine was evaporated under
reduced pressure and the residue dissolved in DCM (150 ml),
washed twice with water (each of 50 ml). The organic layer was
dried (Na2SO4), filtered and evaporated under reduced pressure.
The residue was purified by flash chromatography (1% MeOH
in DCM) to give 6.3 g (65%) of the title compound, mp 72°C.
1HNMR (CDCl3): 1.40-1.57 (m, 13H), 1.98-2.08 (m, 2H), 3.17-
3.50 (m, 6H), 3.70-3.93(m, 4H), 4.04-4.11(m, 1H), 4.59-4.63(d,
2H), 5.02 (bm, 1H), 5.09 (s, 2H), 5.22-5.57 (m, 4H), 5.82-5.99
(m, 1H), 7.32-7.38 (m, 5H), 7.94 (s, 1 H), 8.24 (s, 1H). EIMS:
Acknowledgement. This study was supported by grant RO1
AI27692 from NIAID, NIH, PHS.
REFERENCES AND NOTES
[1] This work dedicated to Prof. Arthur D. Broom in the
occasion of his retirement.
[2] Current address: Department of Pharmaceutical Chemistry,
College of Pharmacy, King Saud University. P.O.Box 2457 Riyadh
11451, Saudi Arabia, email : fadl@aun.edu.eg
[3] Falkiewicz, B.; Kolodziejczyk, A.S.; Liberek, B.;
Wiśniewski, K. Tetrahedron 2001, 57, 7909 and the references sited
therein.
[4] Leijon, M.; Mousavi-Jazi, M.; Kubista, M. Molecular
Aspects of Medicine 2006, 27,160.
[5] Brasuń, J.; Oldziej, S.; Taddei, M.; Kozlowski, H. J. Inorg.
Biochem. 2001, 85, 79.
[6] Mateo-Marť, E. ; Briones, C.; Pradier, C.M.; Mart´ın-Gago,
J.A. Biosens. Bioelectron. 2007, 22, 1926.
[7] Berg, R.H.; Hvilsted, S.; Ramanujam, P.S, Nature 1996, 383,
505.
[8] Falkiewicz, B.; Kowalska, K.; Kolodziejczyk, A.S.;
Wiśniewski, K; Łankiewicz, L. Nucleosides & Nucleotides 1999, 18,
353.
m/z
= 670.50 (M+1); HRMS (FAB): 670.30229(calcd),
670.30015 (found); Anal. Calcd . for C32H43N7O7S: C, 57.37; H,
6.47; N, 14.65; Found: C, 57.16; H, 6.24; N, 14.75.
Nα-(2-Boc-Aminoethyl)-Nα-(1-methyl-6-mercaptopurin-9-
methylcarbonyl)-Nε-CBZ-L-lysine (16). (Ph3P)4Pd(0), (0.23 g,
0.2 mmol) was added to a solution of 15 (1.338 g, 2 mmol) in
THF (100 ml) under argon atmosphere with stirring. Morpholine
(1.76 ml, 20 mmol) was then added drop wise and the stirring
was continued for 4 hours at ambient temperature. The solvent
was evaporated under reduced pressure and the residue washed
with ether (25 ml) then dissolved in ethyl acetate (100 ml). Ether
(50 ml) was added to the resulting solution and the formed
precipitate was collected by filtration. The precipitate dissolved
[9] Falkiewicz, B. Acta Biochem. Pol. 1999, 46, 509.
[10] Ardhammar, M.; Norden, B.; Nielsen, P.E.; Malmstrom, B.
G.; Wittung-Stafshede, P. J. Biomol. Struct. Dyn. 1999, 17, 33.