4908
S. S. Dhaneshwar et al. / Bioorg. Med. Chem. 15 (2007) 4903–4909
in ppm downfield on d scale. The IR spectrum of the
synthesized compound was recorded on JASCO, V-530
FTIR in potassium bromide (anhyd IR grade). The
absorbance maxima (kmax) of synthesized compounds
were determined on JASCO V530, UV–visible double-
beam spectrophotometer in hydrochloric acid buffer
(pH 1.2), phosphate buffer (pH 7.4) and distilled water.
Partition coefficient was determined in n-octanol/phos-
phate buffer (pH 7.4), whereas the aqueous solubility
was determined in distilled water at room temperature
(25 1 ꢁC). Pharmacological screening of the synthe-
sized compound was carried out in the Department of
Pharmacology, Poona College of Pharmacy and its ani-
mal facility is approved by CPCSEA. The experimental
protocols for the same were approved by the Institu-
tional Animal Ethical Committee.
reactions, proper condition of acidity was maintained
throughout, by adding excess of acid (0.5–1 equiv).
The reaction mixture was kept in cryostatic bath at 0–
5 ꢁC during the course of reaction (which is exothermic
in nature), in order to avoid the hydrolysis of diazonium
salt to corresponding phenol.
5.3.4. Coupling of diazotised L-tryptophan methyl ester
with salicylic acid. Coupling of salicylic acid with diazo-
tized tryptophan methyl ester was carried out in situ.
Salicylic acid (0.01 mol) was completely dissolved in so-
dium hydroxide solution (2 mol/ml). The solution was
cooled below 5 ꢁC. Then slowly diazotised salt of trypto-
phan methyl ester was added with continuous stirring,
through syringe. Alkaline condition was constantly
maintained. After completing the reaction, water was
evaporated and crude product was recovered. It was
recrystallized by dissolving in methanol and cooling at
0 ꢁC. Purified product was dried under vacuum. The
reaction was monitored by TLC using chloroform:
methanol (4:1.5), as a solvent system. The route of syn-
thesis is described in Figure 1. Mp 243 ꢁC (uncorrected),
Rf 0.60, IR (KBr) 1487 cmÀ1 –N@N– stretching (non-
symmetric p-substituted azobenzene), 3466–3422 cmÀ1
unbonded phenolic O–H stretching, 3590 cmÀ1 indole
N–H stretching, 1597 and 1383 cmÀ1 carboxylate anion
stretching, 2320 cmÀ1 aromatic C–H stretching,
1030 cmÀ1 C–N stretching. 1H NMR (DMSO-d6): d
6.59 [d, 1H] protons of aromatic OH, d 6.9 [d, 1H]
and d 7.10–7.16 [m, 4H] CH-indole, d 10.65 [d, 1H]
NH-indole, d 6.64 [d, 1H] and d 7.2 [d, 1H] CH-benzene,
d 2.5 [t, 1H] CH-methine, d 2.6 [d, 2H] CH2-methylene.
5.3.2. Synthesis of tryptophan methyl ester hydrochloride
(TMEÆHCl). Freshly distilled thionyl chloride
(0.05 mol + 30% extra) was slowly added to methanol
(100 ml) with cooling and L-tryptophan (0.1 mol) was
added to it. The mixture was refluxed for 7 h at 60–
70 ꢁC with continuous stirring on a magnetic stirrer. Ex-
cess of thionyl chloride and solvent was removed under
reduced pressure giving crude TMEÆHCl. The crude
product was triturated with 20 ml portions of cold ether
at 0 ꢁC, until excess dimethyl sulfite was removed. The
resulting solid product was collected and dried under
high vacuum. It was recrystallized from hot methanol
by slow addition of 15–20 ml of ether, followed by cool-
ing at 0 ꢁC. Crystals were collected on the next day and
washed twice with ether/methanol mixture (5:1) fol-
lowed by pure ether and dried under vacuum to give
pure TMEÆHCl.
Acknowledgment
Mp 220–223 ꢁC (Uncorrected), Rf 0.78 in chloroform/
methanol (2:1), % yield 73. IR (KBr) 3590 cmÀ1 indole
N–H stretching, 1735 cmÀ1 C@O saturated ester stretch-
ing, 1470 cmÀ1 C–H bending CH2, 1430 cmÀ1 and
1370 cmÀ1 C–H bending CH3, 1240 cmÀ1 C–O saturated
Authors are thankful to the AICTE for providing finan-
cial assistance and to Wallace Pharmaceutical Pvt. Ltd.,
Goa, for providing the gift sample of sulfasalazine.
1
ester stretching. H NMR (DMSO-d6): d 10.65 [d, 1H]
NH-indole, d 7.10–7.16 [m, 4H] and d 6.9 [d, 1H] CH-in-
dole, d 4.15 [s, 3H] CH3-methyl, d 2.5 [t, 1H] CH-
methine, d 2.6 [d, 2H] CH2-methylene.
References and notes
1. Meyers, D.; Sachar, D. B. In Medical Therapy of
Inflammatory Bowel Disease; Kersnar, J. B., Shorter, R.
G., Eds.; Williams and Wilkins: Baltimore, 1995; pp 695–
714.
2. Bonner, G. F. South Med. J. 1996, 89, 556.
3. Brzezinski, A.; Rankin, G. B.; Seidner, D. L.; Lshner, B.
A. Clev. Clin. J. Med. 1995, 62, 317.
4. Bonner, G. B.; Ruderman, W. B. In Inflammopharmacol-
ogy; Kluwer Academic: Norwell-Mass, 1993; pp 247–262.
5. Chourasia, M. K.; Jain, S. K. J. Pharm. Sci. 2003, 6, 33.
6. Sands, B. E. Gastroenterology 2000, 118, S68.
7. Sutherland, L. R.; Rothy, D. E.; Beck, P. L. Inflam. Bowel
Dis. 1997, 3, 65.
8. Mahmud, N.; Kamm, M. A.; Dupas, J. L. Gut 2001, 49,
552.
9. Rao, S. S. C.; Read, N. W.; Holdsworth, C. D. Gut 1987,
28, 1474.
10. Takagi, K., Okabe, S.U.S. Patent No., US 3, 1976,
988466.
11. Dhaneshwar, Suneela; Chaturvedi, S. C. Indian Drugs
1994, 31, 374.
5.3.3. Diazotisation of tryptophan methyl ester hydro-
chloride. Tryptophan methyl ester hydrochloride
(0.01 mol) was dissolved in a suitable volume of water
containing 2.5–3 equiv of hydrochloric acid (0.02 mol
of 35% HCl), by the application of heat if necessary
and then solution was cooled in ice. The temperature
was maintained at 0–5 ꢁC on a cryostatic bath and an
aqueous solution of sodium nitrite (2 mol in 10 ml)
was added portionwise, through syringe making sure
that the tip of the syringe was always dipped completely
in the solution. The addition of sodium nitrite solution
was continued until the solution gave an immediate po-
sitive test for excess of nitrous acid with an external indi-
cator, that is, moist potassium iodide-starch paper. The
precipitated tryptophan methyl ester hydrochloride, if
any, got dissolved during the diazotisation to give a
clear solution of the highly soluble diazonium salt. To
stabilize the diazonium salt and to minimize secondary