Belagali, S L

Boja, Poojary

Himaja, M

Kumar, K Harish

NOPR

Indian Journal of ChemistryVol. 37B, April 1998, pp.370 - 375Synthetic and biological studies on 5-(p-chlorophenyl)furan-2-carboxylpeptides and 4-[2'-(5'-formyl)furyl]benzoyl peptidesS L Belagali*, K Harish Kumar, Poojary Boja & M Himaja,Department of P.O. Studies and Research in Chemistry, Mangalore University, Mangalagangotri 574 199, IndiaReceived 21 March 1997; accepted (revised) 5 March 1998Substituted anilines are coupled with furoic acid and furfural at the position-S to get 5-(p-chlorophenyl)furan-2-carboxylic acid and 4-[2'-(5' -formyl) furyl]benzoic acid which on furthercoupling with amino acid esters, di-, tetra- and hexapeptides yield 5-(p-chlorophenyl)furan-2-carboxylamino acid esters and peptides and 4-[2'-(5'-formyl) furyl]benzoyl amino acid esters andpeptides. The structures of these compounds have been confirmed by elemental and spectral analysis.The biological activity of these compounds are reported.Prompted by the varied biological properties ofpeptides', substituted phenyl furan derivatives',bromo furoyl amino acids', nitro furan acryloylamino acid methyl esters', 2-furylacryloylaminoacids and dipeptide derivatives", substituted furanamino acid derivatives' and furan peptides", it wascontemplated to synthesise first aryl substitutedfuroic acid and furyl substituted benzoic acid andthen condense them with different amino acidesters and peptides using DCC as the couplingagent.Diazotised solution of p-aminobenzoic acid withfurfural gives 4- [2'- (5'-formyl)furyl]benzoic acid1 (cf. Scheme I). p-chloroaniline was substituted tofuroic acid at position-5 after diazotisation to give5-(p-chlorophenyl)furan-2-carboxylic acid 2 (cf.Scheme H),which was confirmed by undepressedmixed melting point with authentic samples".For the amino group protection of L-proline, L-phenylalanine and L-valine, di-tert-butylpyrocarbonate (Boc-O-Boc) was used andcarboxylic group of L-proline, t.-valine and L-leucine was protected by converting it in to methylester.Dipeptides N-13oc-Pro-Pro-OMe, N-13oc-Pro-Leu-OMe, N-13oc-Pro-Val-OMe, N-13oc-Val-Val-OMe, N-13oc-Phe-Tyr-OMe were prepared fromthe corresponding amino acid methyl esters and'Boo-amino acids using DCC as a coupling agentand NMM as a base in dichloromethane. Thereaction mixtures were stirred for 24 hr at roomtemperature.The N-13oc group was removed usingCF3COOR/CRCl3 and the methyl ester group wasremoved using LiOR at room temperature.The tetrapeptide N-13oc-Val-Val-Pro-Val-OMewas prepared from dipeptides N-13oc-Val-Val-OMe and N-13oc-Pro-Val-OMe using DCC andNMM after proper deprotection. Similarly,tetrapeptide N-13oc-Val-Pro-Phe-Tyr-OMe wasprepared from dipeptides N-13oc-Val-Pro-OMeand N-13oc-Phe-Tyr-OMe after properdeprotection.The hexapeptide N-13oc- Pro- Pro- Val- Pro- Phe-Tyr-OMe was prepared from N-13oc-Pro-Pro-OMeand N-13oc-Val-Pro-Phe-Tyr-OMe after properdeprotection of the amino and carboxyl groups byusing DCC and NMM as the coupling reagents.4-[2'-(5'-Formyl)furyl]benzoic acid and valinemethyl ester hydrochloride were coupled usingDCC and NMM. The procedure was the same asthat used for the preparation of dipeptides. Theresulting compound was then subjected todeprotection of the methyl ester group using LiORto obtain 4-[2'-(5'-formyl)furyl]benzoyl valine 3a(cf. Scheme III5.The N-13oc group of N-13oc-Pro-Leu-OMe andN-13oc-Pro-Pro-OMe was removed usingCF3COOHI CRCI3. The free carbonyl end of 5'-[formyl)furyl]benzoic acid arid the free end ofdipeptides H-Pro-Leu-OMe and R-Pro-Pro-OMeBELAGALI et aI.: SYNfHETIC & BIOLOGICAL STIJDIES ON SUBSTII1JTED PEPTIDES 371H~C-{ }NHz. _o~> HOZC-<, }'rf_N}Cf>-_b_.:;.> H~C-OVCHO1Reagents.:a = NaNOz./HCl b =~CHO/CuClz.Scheme ICl -<' }NHz. _-=--a~> 0-<, }W.N}Cr--_b_~> Cl-oQ-CDzH2> -0-0-:1II \\OHC I \ CO-X-OHo - 3l-Vol, l-Pro-l-leu, L-Pro-L-Pro, L-Vol-L-Vol-L- Pro-L-VolReagents:b =OHC-O-o-COzH + H-x - OMebWhere, X=Ren q ent s :Scheme IIa > OHCVQ-CO-X-OMea= CHz.Clz., DCC, NMM, 2l,.hrs, RTb = THF: HzO{1:1), LiOH, 1hr, RTScheme illwere coupled to obtain 4-[2'-(5' -fonnyl)furyl]-benzoyl-prolyl- leucine methyl ester 3b and 4-[2'-(5' -formyl) ]benzoyl- furyl-prolyl-proline methylester. The methyl group of the latter compoundwas deprotected using LiOR (cf. Scheme III)to obtain 4-[2' -(5' -fonnyl)furyl]benzoyl-prolyl-proline 3c.The 'Boc-group of N-13oc-Val-Val-Pro-Val-OMe was removed using CF3COOHlCRCl3 andwas coupled with 4-[2'-(5'-fonnyl)furyl]benzoicacid and 5-(p-chlorophenyl)furan-2-carboxylicacid respectively. The resulting compounds weresubjected to methyl ester group deprotection toobtain 4-[2'-(5' -formyljfuryl-benzoyl-valyl-valyl-prolyl-vatine 3d and 5-(p-chlorophenyl)furan-2-carboxyl-valyl-valyl- prolyl- valine 4a( cf. SchemeIV).Similarly 130c deprotected hexapeptide N-13oc-Pro-Pro-Val-Pro-Phe-Try-OMe was coupled with5-(p-chlorophenyl)furan-2-carboxylic acid. Theester group of the resulting compound wasremoved using LiOR to obtain 5-(p-chorophenyl)furan-2-carboxyl-prolyl- prolyl-valyl-prolyl-phenylalanyl-tryptophan 4b (cf. SchemeIV).All the newly synthesized compounds wereconfirmed by elemental analyses and spectral data.Yieldwise, DCC is found to be the good couplingagent.Biological activityThe antifungal and antibacterial activity of allnewly synthesized compounds were tested againstBacillus subtillis, Staphylococcus aureus,Escherichia coli, Pseudomonas aerugirosa and372 INDIAN J CHEM, SEC. B, APRIL 1998Cl-o-O-Co," + "- Y - OMe~ ~eO-Y-OMeCl ~O~a__ b_~> ~ ~eO-Y-OHel~o/(4)Where,Y = L-Val-L-Vol-L-Pro-L-Pro,L- Pro- L - Pro - L - Val- L - Pro - L - Phe. - L - T r pReagent!> :a = eHz( l2' Dee, NMM, 2~ hr s , RTb = T H F : Hz 0 (1:1), L i 0 H I 1 h r I R TScheme IVTable I-Antibacterial and antifungal activity of compounds 1,3a-d and 4a,bZone of inhibition (in mm) at IOJ..LgJconcentrationB.subtillis Siaureus E.coli P.aerugirosa Calbicans09 0907Compd13a3b3c3d4a4b080809 08Candida albicans at 10J.1g1mLin the neutral agarmedia following the disc diffusion method.Solvent control was also run to know the activityof blank solvent. The results are recorded in TableI. It was observed that the antifungal andantibacterial activities of furan derivatives werechanged after coupling with amino acid esters andpeptides.Experimental SectionAll the melting points were taken in opencapillaries and are uncorrected. IR spectra wererecorded on a Perkin-Elmer 137 instrument (Aroaxin cm') and IH NMR in continuous wave mode onan EM-390 (90 MHz) spectrometer (chemicalshifts in 8,ppm) using CDCl3 as a solvent and TMSas an internal standard. Purity of all compoundswere checked by TLC on silica gel G plates.Preparation of dlpeptldes"Amino acid ester hydrochloride (10m moles)was dissolved in CHCl3 (30 mL). To this solution0908o0810090909N-methyl morpholine (35 m moles) was added atO°C. The reaction mixture was stirred for 15minutes. Boc-amino acid (10 m moles) in CH2Cl2(15 mL) and DCC (10 m moles) were added withstirring. After 24 hr, the reaction mixture wasfiltered, concentrated under reduced pressure anddiluted with ethyl acetate. The organic layer waswashed with HCI (10%), NaHC03 (10%) andsaturated NaCI solutions. The organic layer wasdried over anhydrous Na2S04, filtered, andevaporated in vacuum. It was purified byrecrystallization from ethyl acetate / n-hexane.Nstert- Butyloxycarbonyl-prolyl-proline meth-yl ester 1': Dense liquid, yield 60%, IR(CHCI3):3415(br.s), 3250(br.s), 3910(s), 2960(s), 2920(s),2840(m), 1730(m), 1695 (s), 1645(br. s), 1500(br.s), 1380(m), 1360(s), 1160(s), 1085(m), 1010(s)cm', IH NMR (CDCI3, 90 MHz): 8 4.5 (2H, m),3.72(3H, s), 3.5 (4H, m), 2.3-1.9 (8H, m), 1.6-1.5(9H, s).BELAGALI et 01.: SYNfHETIC & BIOLOGICAL STUDIES ON SUBSTITUTED PEPTIDES 373N-tert-Butyloxycarbonyl-prolyl-Ieucine meth-yl ester 2': Pale white crystals, m.p. 93°C, yield66%, IR(CHCI3): 3250(br.s), 2950(s), 1710(s),1700(s), 1620(s), 1510(m), 1420(m), 1380(s), 1360(s), 1160 (s), 1020 (s), 1000(m) cm', IH ?\TMR(CDCI3, 90 MHz): 8 4.2 (IH, 8, J=6.0 Hz), 3.7(3H,s), 2.0-1.9 (2H,m), 1.65 (2H, t, J=6.5 Hz), 1.45(9H,s), 1.35 (IH,m), 1.3-1.1 (6H,m), 1.0-0.8 (6H,d, J=6.5 Hz).N-tert-Butyloxycarbonyl-prolyl-valine methylester 3': White crystals, m.p. 40°C, yield 60%,IR(CHCI3): 3540(br.s), 3310(br.s), 2960(s),2920(m), 2880(s), 1735(s), 1670(s), 1520(br. s),1390(s), 1245(m), 1155(s), 1080(s), 1020(s),770(s) cm";! IH NMR (CDCI3 , 90 MHz): 8 4.3(lH, m), 3.75 (3H, s), 3.5 (lH, m), 3.4 (lH,m), 2.4-1.7 (6H,m), 1.5 (9H, s), 1.5-1.3 (lH, m), 0.9 (6H,d, J=6.0 Hz).N-tert-Butyloxycarbonyl-phenylalanyl-trypto-phan methyl ester 4':White crystals, m.p. 144°C,yield 62%, IR(CHCI3): 3500(br.s), 3400(s),3300(br.s), 2900(s), 1750(s), 1680(m), 1610(s),151O(m), 1360 (s), 1300(s), 1220(s), 1160(m),1010(s), 720(s), 700(s) ern"; IH NMR (CDCI3, 90MHz): 8 7.25-7.0 (IOH, m), 6.85 (lH, br. s),6.4(lH, br.s), 4.85(IH,m), 4.2(IH,m), 3.6 (3H, s),3.2(2H, d, J=6.0 Hz), 3.0(2H, d, J=6.0 Hz),1.4(9H,s).N-tert-Butyloxycarbonyl-valyl-valine met ••y.ester 5': White crystals, m.p. 140°C, yield 63%,IR(CHCI3): 3520(br.s), 3300(br.s), 2960(s),2890(s), 1740(s), 1680(s), 1630(s), 1540(s),1520(s), 1450(s), 1380(s), 1310(s), 1240(s),1120(s), 1100(s), 1020(s)cm-1;', IH NMR (CDCI3,90 MHz): 8 6.5(IH,br.s), 4.6-4.4 (lH, m), 4.2-4.0(IH, m), 3.7(3H,s), 2.7 (IH, br. s), 1.4 (9H, s), 1.4-1.0 (2H, m), 0.95(12H, d, J=7.5 Hz).Preparation of tetrapeptidesN-13oc-Peptide acid (10 m moles), peptide methylester (10 m moles) were dissolved in CHCl3 orTHF. To this solution NMM (35 m moles) wasadded at O°c. The reaction mixture was stirred for15 minutes. DCC (10 m moles) was then addedand stirred for 24 hr. Further work up was done asdescribed for the preparation of dipeptides.N-tert-Butyloxycarbonyl-valyl- prolyl-pbenyl-alanyl-tryptophan methyl ester 6': Dense liquid,yield 61%, IR (CHCI3 ): 3300(br.s), 3020(s),2950(br.s),2900(s), 1730(s), 1640(m), 1510(br.s),1430(s), 1350(s), 1240(s), 1160(s), 1090(s),1030(s), 1000(s), 740(s) cm', IH NMR (CDCI3, 90MHz): 8 7.4-6.9 (10H, m), 6.85 (lH, br. s), 6.6(IH, br. s), 6.5 (IH, br. s), 4.9 (lH, m), 4.7 (IH,m), 4.3 (lH, m), 3.9 (lH, m), 3.65 (3H, s), 3.2 (2H,d, J=6.0 Hz), 3.0(2H, d, J=6.0 Hz), 2.2-1.6 (6H,m), 1.45 (9H, s), 1.35-1.2 (lH, m), 0.9 (6H, d,J=6.0 Hz), l3C NMR (CDCI3 100.4 MHz): 8218(s), 171.6(s), 171.5(s), 170.0(s), 150.8(s),136.1(s), 136.0(s), 128.6(s), 128.5(s), 127.3(s),126.9(d), 123.3(d), 122.0(d), 119.5(d), 118.3(d),114.4(d), 111.3(d), 109.3(d), 79.6(d), 60.0(d),52.8(d), 52.3(d), 49.3(d), 37.6(d), 33.9(t), 31.3(t),30.4(t), 28.3(t), 27.5(t), 25.6(q), 24.9(q), 19.5(q),19.0(q), 17.3(q), 16.9(q).N-tert-Butyloxycarbonyl-valyl-valyl-prolyl-valine methyl ester 7': Dense liquid, yield 60%,IR (CHCI3 ): 3520(br.s), 3400(br.s), 3310(br.s),2990(s), 2950(s), 2920(s), 2840(s), 1730(s),1695(s), 1650(s), 1610(s), 1570(s), 1400(s),1370(s), 1150(s), 1020(s), 81O(s) em:', IH NMR(CDCI3 ,90 MHz): 8 7.15(lH, br.s), 6.8 (2H, br. s),4.7-4.4 (3H, m), 4.2-4.0 (lH, m), 3.7 (3H, s), 3.6-3.3(2H,m), 2.35-1.8 (4H, m), 1.45 (9H, s), 1.35-1.1(3H, m), 0.95 (18H, d, J= 6.0 Hz).Preparation of aryl substituted furoic acidand aryl substituted furfurals/: A mixture ofsubstituted aniline (100 m moles), dil. HCI (15%,60 mL) and water (90 mL) was heated to get aclear solution. The solution was cooled to O°C anddiazotised with NaN02 solution (30%, 24 mL).The diazonium salt solution was filtered and to thefiltrate, water (50 mL) and furoic acid (100 mmoles) / freshly distilled furfural (l00 m moles)and aqueous cupric chloride (2.5 g in 10 mL of"water) were added with stirring. The stirring wascontinued for 4 hr and kept overnight. Theseparated solid was collected by filtration andwashed with cold ethanol. The crude compoundwas recrystallized from a mixture of ethanollDMFto obtain pure aryl substituted furoic acid /arylsubstituted furfural.4-[2' -(5' -Formyl)furyIJ benzoic acid 1: Orangecrystalline solid, m.p. 282°C, yield 85% (Found:C, 66.5; H, 3.7. C12HgO. requires C, 66.7; H,3.7%); IR(CHC13 ): 3706(s), 2820(s), 1676(s),1660(s), 1580(s), 1510(s), 1450(s), 1400(s),1200(s), 1050(s), 1000(s) cm', IH NMR (CDCI3 ,374 INDIAN J CHEM, SEC. B, APRIL 199890 MHz): 8 9.7 (lH, s), 8.3 (2H, d, J= 7.5 Hz),7.95 (2H, d, J=7.5 Hz), 7.35 (lH, d, J=5.5 Hz), 7.0(lH, d, J=5.5 Hz),5-(4' -Chlorophenyl) furan-2-carboxylic acid2: White solid, m.p.197°C, yield 62%, IR (CHC13):2855(s), 1680(s), 1662(s), 1580(s), 1476(s),1416(s), 1260(s), 1094(s), 968(s), 831(s), 792(s)crn', H NMR (CDC13, 90 MHz): 8 9.65(lH,s),7.75(2H,d, J=7.5 Hz), 7.4(2H,d, J=9.0 Hz),7.3(lH,d, J=5.5 Hz), 6.8(lH,d, J=5.5 Hz).N-tert- Bu tyloxycarbo nyl-p rolyl-prolyl- valyl-prolyl-phenylalanyl-tryptophan methyl ester 8':Dense liquid, yield 50%, IR(CHC13 ): 3460(br.s),3380(br.s), 3190(br.s), 2950(s), 2900(s), 1730(s),1650(m), 1500(m), 1440(s), 1385(s), 1355(s),1315(s), 1265(s), 1235(s), 1155(s), 1110(m),1080(m), 920(m), 880(m), 855(m), 760(br.s) cm',IH NMR (CDC13 , 90 MHz): 8 7.4-6.9 (lOH, m),6.8-6.2 (4H, m), 4.9-4.0(6H,m), 3.6-3.4 (4H, m),3.2 (2H, d, J=6.5 Hz), 3.0 (2H, d, J=7.0 Hz), 2.2-1.5 (l8H, m), 1.4 (9H, s), 1.3-1.0 (lH, m),0.9(6H,d, J=7.5 Hz), FABMS: mJz 856(M+l, 3%),831(5), 781(l0), 684 (35),562(80),306 (62),219( 58), 201 (68), 120( 100), 70(82).4-[2' -(5' -formyl) furyl] benzoyl-valine 3a:Semisolid, yield 80%, (Found: C, 64.6; H, 5.4; N,0.3. C17H1705Nrequires C, 64.8; H, 5.5; N, 0~3%),IR(CHC13): 3100(br.s), 2900(s), 2820(s), 1720 (br.s), 1660(br.s), 1570(s), 1360(s), 800(s) em", IHNMR (CDC13, 90 MHz): 8 9.7 (lH, s), 7.9 (2H, d,J=7.5 Hz), 7.6 (2H, d, J=7.5 Hz), 7.35(IH, d, J=4.0Hz), 6.9 (lH, d; J=4.0Hz), 6.3 (IH, br. s), 4.2 (lH,m), 1.5-1.3 (IH, m), 0.96 (6H, d, J=6.5 Hz).4-[2' -(5' -formyl) furyl]benzoyl-prolyl-Ieucinemethyl ester 3b: Semisolid, yield 78%, (Found: C,65.3; H, 6.3; N, 6.3. C24H2s06N2requires C, 65.5;H, 6.4; N, 6.4%), IR (CHC13 ): 3360 (br.s),3000(s), 2960(s), 1760(s), 1720(s), 1680(s),l560(s), 1480(s), l400(s), l280(s), 1080(s) crn', IHNMR (CDC13, 90 MHz): 8 9.7 (IH, s), 7.9 (2H, d,J= 7.5 Hz), 7.6 (2H, d, J=7.5 Hz), 7.35 (IH, d,J=4.0Hz), 6.9 (lH, d, J=4.0 Hz), 6.4 (lH, br. s),4.5 (lH, m), 4.25 (lH, m), 3.7 (3H, s), 3.5-3.1(2H,br. m), 2.32-1.5(6H, m), 1.3-1.1 (IH, m), 0.95 (6H,d, J=6.0Hz).4-[2' -(5' -Formyl)furyl] benzoyl- prolyl-proline3c: Semisolid, yield 76%' (Found: C, 69.9; H, 5.3;N, 7.0.; C22H2206N2requires C, 69.0; H, 5.4; N,7.1%), IR(CHC13): 3080(s), 2890(s), 2800(s),1670(s), 1650(s), 1580(s), 1500(s), 1450(s),1350(s), 1320(s), 1220(s), 830(s) em", IH NMR(CDCI3, 90 MHz): 8 9.7(IH,s) 7.9 (2H, d, J=7.5Hz), 7.6 (2H, d, J=7.5 Hz), 7.35 (IH, d, J=4.0 Hz),6.9 (lH, d, J=4.0 Hz), 4.2 (2H, m), 3.6-3.1 (4H,m), 2.2-1.6 (8H, m).4-[2' -(5' -Formyl)furyl] benzoyl- valyl-valyl-prolyl-valine 3d: Semisolid, yield 82%, (Found:C, 62.1; H, 6.7; N, 9.3. C31H420sN4 requires C,62.2; H, 7.0; N, 9.4%), IR (CHC13): 3360(br.s),3000(s), 2880(s), 1720(s), 1700(br.s), 1680(s),1580(s), 1560(s), 1480(s), 1400(s), 1360(s),1240(s), 780(s) cm', IH NMR(CDC13, 90 MHz): 89.7 (lH, s), 7.9 (2H, d, J=7.5 Hz), 7.6 (2H, d,J=7.5 Hz), 7.35 (lH, d, J=4.0 Hz), 6.9 (IH, d,J=4.0 Hz), 6.4-6.2 (3H, br. s), 4.3-3.9 (4H, m), 3.6-3.2 (2H, m), 2.1-1.6 (4H, m), 1.3-1.1 (3H, m), 0.95(18H, d, J=6.0 Hz).5 - (4' -Chlorophenyl)furan-2-carboxyl-valyl-valyl-prolyl-valine 4a: Semisolid, yield 82%,(Found: C,60.2; H, 6.7; N,9.0. C31H4107N4Clrequirers C, 60.3; H, 6.6; N, 9.1 %), IR (CHC13):3360(br.s), 3000(s), 2880(s), 1720(s), 1700(s),1680(s), 1580(s), 1560(s), 1480(s), 1400(s),1360(s), 1240(s), 780(s) cm', IH NMR(CDC13, 90MHz): 8 8.3 (2H,d, J=7.5 Hz), 7.7 (2H, d, J=7.5Hz), 7.2(lH, d, J=5.0 Hz), 7.0(lH, d, J=5.0 Hz),6.4-6.2(3H, br.s), 4.3-3.9(4H,m), 3.6-3.2(2H, m),2.1-1.6( 4H,m), 1.3-1.1 (3H,m), 0.95(18H,d,J=6.0Hz).5 - (4' -Chlorophenyl)furan-2-carboxyl-prolyl-prolyl-valyl-prolyl-phenylalanyl-tryptophan 4b:Semisolid, yield 78%, (Found: C, 64.4; H, 5.9; N,10.2. C51H1709N7Clrequires C, 64.6; H, 6.0; N,10.4%), IR (CHC13): 3360(br.s), 3300(br.s),3120(br.s), 2900(s), 2850(s), 1750(br.s),1650(br.s), 1620(s), 1560(s), 1450(s), 1360(s),1310(s), 1240(s), 1100(s), 880(s) cm', IH NMR(CDC13, 90 MHz): 8 8.3(2H, d, J=7.5 Hz), 8.1-7.9(5H, m), 7.7 (2H, d, J=7.5 Hz), 7.6-7.4 (5H, m),7.2 (IH, d, J=5.0 Hz), 7.0 (IH, d, J=5.0Hz), 6.9(2H, br. s), 6.1 (2H, br. s), 4.6 (3H, m), 4.0 (3H,m), 3.4-3.2 (4H, m), 3.2-2.9 (6H, m), 2.2-1.6 (12H,m), 1.4-1.2 (lH, m), 0.95 (6H, d, J=6.0 Hz).AcknowledgementThe authors are thankful to Prof. Ramana,Department of Pharmaceutics, NGSM College ofPharmacy, Deralakatte for the antifungal andBElAGALI et al.: SYNTIIETIC & BIOLOGICALSTIJDIES ON SUBS11TIJfED PEPTIDES 375antibacterial screening of the newly synthesizedcompounds.References1 Wadsworth W S, J Org React, 25, 1977,73.2 Alekseeva L N, Kruzmetra L, Zile A & Frimm R, Latv P SR Zinath Akad Vestis, 12, 1968, 129 ; Chern Abstr, 1969,65551v.3 EI-Nagger A M, Ahmed F S M, Abd El-Salam A M, EJ-Gazzar, M A & Ibrahim T M, Egypt J Chern, 23(3),1980,209.4 El-Nagger A M, Ahmed F S M, Abd El-Salam A M, El-Shami M S, Egypt J Chern, 26(1),1983,75.5 Ayalap Abidin, Pak J Pharm Sci, 3( I), 1990, 21.6 Rai U K, Shanker B, Singh S & Balaji Rao, Indian J Chern,32B, 1993,621 .7 Oda R, Mem Fac Eng, Kyoto Univ, 14, 1952, 195 ;ChernAbstr, 48,1954, 1935.8 Bodanszky M & Bodanszky A 'The Practice of peptidesynthesis (Springer-Verlag, New York), 1984, pp 91, 145 &209.9 Akashi H & Oda R, Rept Inst Chern Research Kyoto Univ,19,1943,93.

Synthetic and biological studies on 5-(p-chlorophenyl)furan-2-carboxyl peptides and 4-[2'-(5'-formyl)furyl]benzoyl peptides

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Synthetic and biological studies on 5-(p-chlorophenyl)furan-2-carboxyl peptides and 4-[2'-(5'-formyl)furyl]benzoyl peptides

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