May 1967
I R R E V E R S I B L E ESZYJIE I N H I B I T O R S .
white crystals, mp 235-240°, lit.lO nip 233', with unchanged nltraviolet spectra. The filtrate from the 1-benzyl-6-methyluracil was extracted with four 50-ml portions of CHCl,. The combined estracts were washed with 50 ml of water, dried (RIgSOd), then spin evaporated in uacuo; yield, 0.458 g (2154) of 3-benzyl-6-methyluraci1, mp 160-172" ; this was essentially free of 1-benzyl-6-methyluracil since it had A, ( p H 7 ) , 264 m p ; ( p H 13), 282 mp. Recrystallization from ethyl acetate gave 0.417 g (19%) of fairly pure :3-benzyl-6-methyluracil, mp 177-183", lit.1o mp 194", but with unchanged ultraviolet spectra. Similarly, benzylation of 2.10 g (15 mmoles) of 5,6-dimethy[uracil (Aldrich Chemical Co.) gave 290 mg (18:;) of the 1,3dibenzyl derivative as an oil that was uniform on tlc and had hmax( p H 7 , 13) 280 mp. Acidification of the alkaline solution gave 230 mg (20%) of 3-benzyl-5,6-dimethyluracil~mp 196-201 O, that was recrystallized from ethyl acetate; see Table 1- for additional data. By chloroform extraction of the aqueous filtrate was isolated 535 mg (24%) of l-benzyl-5,6-dimethyluracil that had Ama, ( p H 7), 273 mp; ( p H 13), 278 m p , indicating some contamination with the 3-benzyl isomer. Recrystallization from benzenepetroleum ether ( b p 38-52') gave 148 mg ( 6 . 7 5 ) of more pure 1 isomer, mp 173-184", Amax ( p H 7 , 13) 274 mp. Method J.-.4 solution of 144 mg (0.5 mmole) of V in 5 ml of isoamyl alcohol containing 25 p1 of 12 &Vaqneous HCl was heated a t 75' for 2.5 hr, then spin-evaporated in L'UCUO. Crystallization from petroleum ether ( b p 60-110') gave 150 nig ( 9 1 q ) of lyhite leafs, mp 87-88', that moved as one spot on tlc in petroleum ether ( b p 60-110°)-ethy1 acetate (4:6). See Table 1. for analytical data on this product (VII).
LxxyIII
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5-n-Amyl-3-(2,4-dinitrobenzenesulfenyl)-6-n-propyluracil (XXVIII).-To a solution of 1.12 g ( 5 mmoles) of 5-n-amyl-6-npropyluracil in 5 ml of reagent pyridine was added 1 . l i g uf 2,4-dinitrobenzenesulfenyl chloride. .Ifter 2 hr a t ambient temperature, the solution was diluted with 20 ml of ice water. The product was collected on a filter, washed with water, dried, and recrystallized from ethyl acetate: yield, 1.6 g (76%) of yellow needles; mp 203-204"; Am,, (ethanol), 275, 315 nip (plateau); ( p H la), 320 mp: vmas 3200, 2950 (NH), 1710, 166I), 1640, 1590 (C=O, XH, C=C), 1520, 1340 cm-I (NO2). Anal. Calcd for C I S H ~ Z ~ ~ ' ;C, ~ O51.2; & : H, 5.25; Tu', 13.3, S, 7.59. Found: C, 50.9; H, 5.28; X, 13.1; S,7.39. 5-Hydroxymethyl-1-phenylpropyluracil(IV).--Anhydrous HBr was slon-ly bubbled through a solution of 2.88 g (10 mmoles) of .5-ethosymethyl-l-phenylpropyluracil (V)in 50 ml of CH2Cls for 30 min; a pilot experiment followed by tlc showed that 110 V remained at this time. The solution was diluted wlth 50 nil of CH2CIz, then washed with two 50-ml portions of water. Spin evaporation in Z'UCZLO left a mixture of IT and the bromomethyl derivative ( S S I I I b ) . The residue was refluxed in a solution of 100 ml of 50% aqueous T H F for 3 hr, then the solrrtion n-as spin evaporated in z"xo to about 25 ml. After several hours a t 3", the mixture was filtered and the product was washed with water; yield, 1.86 g (72%) of crude product, mp 140-142'. Recrystallization from acetone XTith the aid of decolorizing carbon gave 1.44 g ( 5 6 5 ) of white crystals, mp 151-152'; the conipouiid moved as a single spot on tlc in ethyl acetate and had A,, (alcohol), 272 m p : ( p H 13), 269 mp; vma, (pl'ujolj 3330, 3150 ( S H ) , 1iO0, 1670, 1600 (C=O, C=C, XH), 735, 695 c n - 1 (C&). Inal. Calcd for CI,H,sS,03: C, 64.6; H, 6.20; S, 1O.S. Found: C, 64.7; H, 6.40; S , 10.6.
Irreversible Enzyme Inhibitors. LXXVIII.1v2 Inhibitors of Thymidine Phosphorylase. IV.' Hydrophobic Bonding by Cracils Substituted a t the 5 and 6 Positions B. R. BAKER AND ~IITSUTAKA I y .XI1 than may be due to its o n t - o f plane ti-phrn~-lg r o u p . f 14) r. Heidelherger and .I. l$iioiiar. R r o r h i m . E i o p h g s . d r t r i . 91, 6:ik (lW4I.
May 1967
IRREVERSIBLE EXZIXEIXHIBITORS.L X X I X
the clesired 6-phenethyluracil (IX). Similarly, 6phenylpropyluracil (X) was synthesized from 4-phenylbutyric acid via ethyl y-phenylbutyrylacetate and 6phenylpropyl-2-thiouracil.
Experimental Section17 6-(Phenylpropyl)-2-thiouraciI.-Ethyl y-phenylbutyroylacetate, bp 138-140" ( 2 mm), was synthesized as described for ethyl P-phenylpropionylacetate, then condensed with thiourea as described for 6-phenethyl-2-thio~iracil.~~ Recrystallization from dioxane gave a 71Yc yield of white prisms: mp 201-203'; Am,= ( p H 6), 275 mp; ( p H 13), 260, 291 mp. ;Inal. Calcd for C13H14X2SO: C, 63.4; H, 5.73; X, 11.4. Found: C, 63.7; H, 5.93; N, 11.2. 6-Phenethyluracil (IX).-A mixture of 4.5 g (18 mmoles) of 6phenethyl-2-thiouracil,16100 ml of water, and 5 g of chloroacetic acid was refluxed with stirring for about 18 hr. The cooled mixture was filtered and the product was washed with water. Recrystallization from water gave 3.3 g (777,) of white plates: mp 260-262": Am,= ( p H 7 ) , 263 mp: ( p H 13), 2i8 mp. d n a l . Calcd for C1,HI2N2O2:C, 66.7; H, 5.59; S , 13.0. Found: C, 66.8; H, 5.65: Tu', 12.8. 6-Phenylpropyluracil (X).-Hydrolysis of 6-phenylpropyl-2thiouracil as decribed for the preparation of IX gave, after recrystallization from 30% acetic acid, an 857, yield of white ( p H 6), 263; ( p H 13), 278 mp. leaflets: mp 145-147'; A,, Anal. Calcd for C13H14x202: C, 67.9; H, 6.13; N, 12.2. Found: C, 68.2; H, 6.33; X, 12.1. 6-(p-Nitrobenzyl)uracil (XIIL).-To a stirred mixture of 6 ml of 96c7, H2S04and 6 ml of 70% H I 0 3 a t 50" was added over 10 min 1.30 g (6.45 mmoles) of 6-benzyluracil (T-III).z The solution ( l i ) Melting points were determined %it11a Fischer-Johns apparatus and those below 230' are corrected. Ultraviolet spectra aere determined in 107, ethanol (unless otherwise indicated) with a Perkin-Elmer 202 spectropliotometer. Infrared spectra were determined with a Perkin-Elmer 13TB spectrophotomete'. in KBr pellets. Kmr spectra were run in D3ISO with a Yarian -1.60 using (CHa)PSi as an internal standard. .\I1 compounds vere uniform on thin layer chromatography on Brinkmann silica gel G F when spots were detected b y &ual examination under ultraviolet light.
313
was cooled to 25" and stirred for an additional 20 min, then poured into a large volume of iced water. The product was collected on a filter and washed with nFater. Recrystallization from dimethylformamide gave slightly yellow prisms: yield 1.0 g (63%); mp 277-278' dec; umsx 1750, 1650 (C=O, C=S, S H , C=C), 1520, 1350 cm-1 ( N O Z ) ; Amax ( p H 7 ) , 267 nip; ( p H 13), 285 mp; pK, = 9.1 (spectrophotometric); 7 1.80, 1.93, 2.40 2.53 (4 protons, CsH4),4.78 ( 1 proton, uracil 5-H). dnal. Calcd for CllH&304: C, 53.4; H, 3.67; S, 17.0. Found: C, 53.2; H, 3.73; S, 17.2. Since uracil has pK, = 9.5 and 5-nitrouracil has pK, = 5 . 3 , ' b the observed pK, of XI11 indicates the nitro group is not at the 5 position of the uracil. Similarly, 5-nitro-6-methyluracil has Am,, 370 mp ( p H 13), which is shifted 95 mp to longer wavelength than that of 6-methyluracil. Since 6-benzyluracil haa A,, 292 mp ( p H 13), the observed Amax of XI11 indicates the nitro group is not at the 5 position of the uracil. 6-(p-Nitrophenyl)uraeil (XV).-Nitration of 6-phenyluracil (VII)2 as described for the preparation of XIII, then recrystallization from aqueous dioxane, gave a 61% yield of product as light ( p H 6), 273 mp; (pH 13), yellow prisms: mp 296-297"; A,, 305-310 mp (shoulder); T 1.81, 1.94, 2.40, 2.53 ( 4 protons, CeHd), 4.78 (1 proton, uracil 5-H). I n a l . Calcd for CloHsTu'304: C, 51.5: H, 3.03; S, 1X.O. Found: C, 51.7; H, 3.20; ?J, 17.9. 6-(p-Aminobenzyl)uracil (XIV) Hydrochloride.--A solution of 1.23 g ( 5 mmoles) of XI11 in 50 ml of glacial acetic acid Jyas shaken with hydrogen at, 2-3 atm in the presence of 200 mg of 5% Pd-C for 1.5 hr when reduction was complete. The filtered solution was spin evaporated in z~acuo. The residue was dissolved in 57, aqueous HC1. After clarification of the solution with decolorizing carbon, the solution was spin evaporated in z"m. Recrystallization of the residue from ethanol gave 0.80 g (637,) of white prisms: mp 293-295': vmax 3250 ( S H ) , 1710, 1680, 1520, 1495 cm-l (C=O, C=C, C=K, N H ) ; A,,, (pH i),238 (shoulder), 263 mp; ( p H 13)) 285 mp. Anal. Calcd for C11HllX302~HC1: C, 52.1; H, 4.76; S, 16.6. Found: C, 51.8; H, 5.00; S, 16.4. The free base had mp 263-264". (18) D. J. Brown, "The Pyrimidines," Interscience Puhlishers, Inc., New I'ork, N . Y., 1962, pp 472-4i6.
Irreversible Enzyme Inhibitors. LXXIX.1'2 Inhibitors of Thymidine Phosphorylase. V.' Mode of Pyrimidine Binding €3. R. BAKER ASD ;\IITSUTAKA I
