`/.f.''-:'·•
`,~·::·' ."
`
`..,..,.
`
`.t~;..---~
`
`'
`
`,G.9..b
`
`1'~- 22.3.il
`·~~71
`
`1'
`
`I
`
`I'
`
`168,43c
`
`52.70
`
`169, t 2C
`
`42.38
`
`142.58
`
`127.271,h
`12a.271,h
`
`126.89
`
`122.15
`(C4• or Cr)
`122.32
`(C4• or C7)
`123.45 (C3•)
`124.37
`(Cs• or Ca1
`124.41
`(C5• or Cs•)
`138.84
`(C3•a ·or C7'a)
`138.95
`(C3•a or C1•a)
`142.58 (C2'1
`
`_.
`0 _.
`
`i]ak OCH3
`
`23.03
`
`187.91
`
`78.94
`
`171.57
`
`.43,51
`
`1-37.45
`
`afilzk
`
`OCH2CH323.25 16B. 13
`
`77.43
`
`t7L29
`
`43.60
`
`137.57
`
`127.701,h
`128.701,h
`
`127,69h,1
`12a,79l,h
`
`127.62
`
`55.84 (CH3)
`
`127.691
`
`15.0S(CH3)
`64.51 (CH2)
`
`8 Tho 13c NMR spootra were la.ken In DMSO-d6 unless otherwise lodlca!9d. The number -ln each entry ls the c:horfilc:al shlrt Vl'l!Uo In pe.rls P4f
`rolaHve lo JMS, The number Jn par1~nthoE1ses Jn si;ilocl cates Is 1he proposed asslgnmen\, b Rel, GB, e,d,o ThosG sols ol poaks rnay bGo
`mllfion
`the lnlens~y of noa-rby peaks. 0 These poaks may bo lnlerChangeablo. h Tho close pro:d·
`f The pe-ak had approximately lwk:e
`Interchangeable.
`I The remalrilng aromaHc airbon algnal.s (125,50, 126.00,
`the ~ peaks did net permit
`ihe assJ;Jnment or these rl)sonal"ICas,
`lmtty ol
`I R11f. 104,
`126.10, 126.30, 126.SO. 127.50, 127.70, 127.90, 132.40, 132.SO, 136.50) we1re not a.sa!Qnetd due lo their alrn~lar chemk::al shift veluos, k The 13 C
`I ThEt peak had approxlmately 1hroo 1lmo 1he
`lnlensh:y of. naarby peak.s.
`NMA speclfa were
`taken
`In CDCl3,
`
`
`
`102
`
`The chemical shifts values observed
`
`for
`
`the heterocyclic carbon
`
`atoms provided strong support
`
`for
`
`the proposed substitution site in
`
`this portion of
`
`the molecule.
`
`In all cases, the chemical shift value
`
`for
`
`the substituted aromatic carbons was downfield (6.0 - 20.0 ppm)
`
`versus
`
`the corresponding signal in
`
`the unsubstituted heterocycle.
`
`This
`
`trend was consistent with previous observations.158
`
`3.
`
`Pharmacological Evaluation.
`The 2-substituted-2-acetamido·N-benzylacetamides .6..9. and fill.
`
`prepared in this study were submitted
`
`to
`
`the Eli Lilly Corporation,
`
`Indianapolis,
`
`Indiana,
`
`for evaluation of
`
`their anticonvulsant activity.
`
`The previous
`
`results obtained by Kohn and co-workers68, 102,
`
`for
`
`related compounds suggested
`
`that
`
`these substances ·would be most
`
`active
`
`in · the MES seizure test.
`
`Accordingly, only
`
`this anticonvul-
`
`sant screening procedure was conducted. Each of
`
`the substances
`
`were administered
`
`intraperitoneally at
`
`three doses (300, 100 and 30
`
`mg/kg)
`
`to groups of
`
`four mice (male albino, CF-1 strain).
`
`Those
`
`compounds which were
`
`found
`
`to be effective
`
`in . the protection of
`
`seizures
`
`induced by electrical stimulation were
`
`further tested with
`
`better monitoring of dosages in groups of twelve mice. This pro(cid:173)
`
`cedure permitted
`
`the determination of
`
`the Effective Dose (ED) 50
`
`value for the drug candidate. This value
`
`is the dose which is effec(cid:173)
`
`tive
`
`in protecting 50 % of
`
`the animals
`
`tested against seizures.
`
`In
`
`addition
`
`to
`
`this
`
`test.
`
`the neurologic toxicity (TOX) of some of the
`
`biologically active compounds was evaluated by means of
`
`the
`
`
`
`103
`
`horizontal screen
`
`test using
`
`the same conditions
`
`(dosages, number
`
`of
`
`animals
`
`tested) employed
`
`in
`
`the ED 50 determination.
`
`This
`
`procedure permitted
`
`the calculation of
`
`the Toxic Dose (TD) 50
`
`value which corresponds
`
`to the dose
`
`that
`
`leads to toxic manisfes(cid:173)
`
`tations
`
`in 50 % of the animals screened. Tables 31 - 34 summarize
`fill., rui and
`
`results observed
`
`for compounds
`
`the pharmacological
`
`some clinically used anticonvulsant agents.
`
`For
`
`the purpose of
`
`the discussion of
`
`the
`
`results, several
`
`assumptions have been made. First,
`
`it is assumed that each sub(cid:173)
`
`strate
`
`is in'fluenced
`
`to
`
`the same degree by
`
`the many processes
`
`(i.e., absorption, distribution, metabolism, elimination) which affect a
`
`drug's
`
`action
`
`from
`
`the
`
`time
`
`it
`
`is administered to
`
`the time the
`
`biological response occurs.
`
`Second,
`
`it is assumed
`
`that
`
`the active
`
`agent is
`
`the substrate itself and not a metabolite of the com-
`
`pound.
`
`No
`
`tests were conducted
`
`to verify
`
`the validity of these
`
`assumptions.
`
`The 2-acetamido-N-benzylacetamides bearing a
`
`five mem(cid:173)
`
`bered
`
`ring heteroaromatic at
`
`the a.-carbon
`
`(69 a-d) (Table 31) all
`
`displayed outstanding anticonvulsant properties
`
`in the MES seizure
`
`test. Within
`
`this series,
`
`derivatives were more potent than
`
`the 2-pyrryl {fill.)
`the 2-furyl (fil!a) and
`the parent aromatic substrate fill.!:!,
`
`and 3-thienyl {filld.) adducts were
`
`less
`
`while
`
`active
`
`the 2-thienyl (fill.lj
`than filill.
`
`activity similar
`
`to phenytoin
`
`under comparable conditions.
`
`(Table 34)
`
`Of particular note, ~ and
`.6..a,b. exhibited
`tu.al and diazepam (2.$)
`Of these two medicinal agents,
`
`
`
`104
`
`Table 31. Pharmacological Evaluation of 2-Substituted-2-acetamido-N(cid:173)
`benzylacetamides (fill.) Containing a Monocyclic Heterocyclic Moiety.a
`
`0 YH
`
`R
`-~ N~Ph
`0
`
`69
`
`No.
`
`fillli.d
`
`2.9.a
`
`69b
`
`filkf
`
`.!ill.d.f
`
`R
`
`Phenyl
`
`2-Furyl
`
`MESb, ED50
`
`ToxC, TD50
`
`32.1 (27.5 - 40.2)
`
`10.3 ( 9.1 - 11.6)
`
`> 4oe
`
`-40
`
`2-Pyrryl
`
`16.1 (13.2-19.9)
`
`30 - 100
`
`2-Thienyl
`
`44.8 (38.9-51.4)
`
`30 - 100
`
`3-Thienyl
`
`87.8 (69.9 - i 50.0)
`
`> 100
`
`and TOSO
`a The compounds were administered intraperitoneally. ED50
`are in mg/kg. The number
`in parentheses are the 95 % confidence
`0 Maximal electroshock seizure
`intervals.
`test.
`c
`Horizontal
`screen
`test
`(neurotoxicity) unless otherwise
`indicated. d Ref. 162.
`eRotarod ataxia test. f Ref. 104.
`
`;, ..
`_:~ .
`
`' '
`
`' i
`. ' !
`
`
`
`105
`
`Table 32. Pharmacological Evaluation
`benzylacetamide
`(Jill) Containing a
`Moiety.a
`
`of 2-Substituted-2-acetarnido-N(cid:173)
`Benzo-fused Heteroaromatic
`
`69
`
`No.
`
`R
`
`MESb, EDSO
`
`ToxC, TOSO
`
`~d
`
`~-Naphtyl
`
`> 300
`
`> 300
`
`filli
`
`£.9.Q.
`
`fillli
`
`2-Benzoluryl
`
`> 100, < 300
`
`> 100, < 300
`
`3-lndolyl
`
`>300
`
`< 300
`
`2-Benzo[b]thienyl
`
`> 100, < 300
`
`> 100, < 300
`
`aThe compounds were administered intraperitoneally. EDSO and. TOSO
`are
`in mg/kg.
`b Maximal electroshock seizure
`test. c Horizontal
`screen
`test
`(neurotoxicity). d Ref. 104.
`
`
`
`106
`
`;:i;:i. Pharmacological Evaluation of 2-Alkoxy-2-acetamido-.~.-
`Tabla
`benzylacetamide ®).a
`
`R
`0 ~H
`~N . N~h
`H
`0
`
`86
`
`R
`
`CH3
`
`MESb, ED50
`
`ToxC, TD50
`
`51.0 ( 46.6 - 58.6}
`
`> 1ooe
`
`CH2CH2SCH3
`
`> 100, < 300
`
`CH(CH3}2
`
`> 100, <300
`
`g
`
`g
`
`OCH3
`
`OCH2CH3
`
`98.3
`
`< 300
`
`..
`
`62.0( 51.1 - 78.4}
`
`> 112
`
`No.
`
`68ad
`
`filkf
`
`filillf
`
`1lli.9.
`
`.!llib.
`
`aThe compounds were administered intraperitoneally. ED50 and TD50
`in mg/kg. The numbers
`in parentheses are the 95 % confidence
`are
`intervals.
`b Maximal electroshock seizure
`test. c Horizontal . screen
`test (neurotoxicity) unless otherwise indicated. d Ref. 104. e Rota rod
`f Ref. 68.
`g These values were not determined.
`ataxia test.
`
`
`
`107
`
`Table 34. Pharmacological Activity of Some Proven Anticonvulsants.a
`
`No.
`uact
`~d
`
`.u12e
`
`15.ae
`
`2.6.e
`
`Name
`
`MEsb •. EDSO
`
`ToxC, TDSO
`
`Phenytoin
`
`Diazepam
`
`Metphenytoin
`
`14.0
`
`18.7
`
`61.0
`
`Phenobarbital
`
`20.1
`
`Valproic Acid
`
`664.8
`
`86
`
`57
`
`154
`
`97
`
`1264
`
`aThe compounds were administered intraperitoneally. EDSO and
`TOSO
`in mg/kg. b Maximal electroshock seizure test. c Rota rod ataxia
`are
`test (neurotoxity). d Ref. 162. e Ref. 163.
`
`
`
`108
`
`phenytoin
`
`(1.aa)
`
`is the most widely prescribed drug
`
`today for the
`
`treatment of . epilepsies.
`
`Examination of
`
`the TD 50 values
`
`for
`
`the
`
`rnonocyclic
`
`heteroaromatic adducts
`
`!2.9_
`
`indicated
`
`that neurologic
`
`toxicity closely
`
`paralleled
`
`their activity
`
`in
`
`the MES
`
`·seizure
`
`test.
`
`· The TD 50 value
`
`for
`
`the most active compound,
`
`the furyl
`
`derivative .fillll , was approximately 40 mg/kg.
`
`The observed data
`
`permitted several
`
`tentative conclusions.
`
`First, compounds 69 a-d
`
`like filll1. all contain an electron
`
`rich
`
`it-aromatic system.
`
`Second,
`
`all of the heteroaromatic substituents at
`
`the u'carbon were rela-
`
`tively small. Moreover, within
`
`this series of
`
`five compounds
`
`the
`
`smallest analogues (fill.a, Jillb.) were
`the most active.
`ring heteroaromatic compounds Jill.1:h, as
`
`All of
`
`the
`
`fused
`
`well as
`
`the parent naphtyl adduct fill.a (Table 32) were considerably
`
`less active than their monocyclic counterparts (Table 31 ).
`
`None
`
`displayed significant activity at dosages below 100 mg/kg. Of
`
`these
`
`compounds,
`
`the 2-benzofuryl
`
`(filill and the 2-benzo[b]thienyl (fillh)
`
`derivatives were
`
`the most potent agents.
`
`The dramatic decrease
`
`in biological activity versus
`
`their monocyclic counterparts suggested
`
`that stringent steric
`
`requirements may exist
`
`for maximal biological
`
`activity.
`
`The 2-acetamido-N-benzyl-2-alkoxyacetamides Jill. intermediates
`
`utilized
`
`in
`
`the
`
`synthesis
`
`of many
`
`of
`
`the
`
`heteroaromatic
`
`functionalized amino acids derivatives (Method B) were also sub(cid:173)
`
`mitted
`
`for
`
`pharmacological
`
`testing
`
`(Table 33).
`
`Included
`
`in
`
`this
`
`table
`
`are
`
`several alkyl and substituted alkyl analogues which
`
`
`
`109
`
`serve as suitable
`
`reference eompounds.
`
`Both
`
`the 2-methoxy (Jlfua)
`
`and
`
`the 2-ethoxy (.flfil2) derivatives exhibited notable activity
`
`in
`
`the
`
`MES
`
`seizure
`
`test.
`
`The pharmacological
`
`activity of ruill. was
`
`comparable
`
`to metphenytoin (1.:ib.) under similar · conditions.
`
`The
`
`limited
`
`results
`
`secured
`
`from
`
`this series of compounds do not
`
`permit us to make any tentative conclusions concerning
`
`the role of
`
`the oxygen atom in modulating
`
`the biological activity of
`
`these
`
`derivatives.
`
`The composite set of data (Tables 31 • 33) suggests that
`
`stringent
`
`steric
`
`constraints exist at
`
`the
`
`receptor site
`
`for drug
`
`binding.
`
`Moreover, among
`
`the
`
`four monocyclic heteroaromatic
`
`compounds,
`
`the pharmacological
`
`. activity
`
`increased with decreasing
`
`resonance stability of
`
`the aromatic moiety.
`
`This trend suggests
`
`that
`
`the biological activity
`
`is modulated
`
`by
`
`the ability of
`
`the
`
`drug candidate· to bind with an electrophilic site at
`
`the
`
`receptor.
`
`:r:r:r.
`
`Experimental Section. General Methods. Syntheses. Melting
`
`points were determined with a Thomas-Hoover melting point apparatus and
`
`are uncorrected.
`
`Infrared spectra (IR) were run on a Perkin-Elmer 1330
`
`spectrophotometer and calibrated against the 1601 cm·1 band of polystyrene.
`
`Absorption values are expressed in wavenumbers (cm· 1 ). Proton nuclear
`
`magnetic resonance (1 H NMR) and carbon nuclear magnetic resonance
`
`(13c NMR) were _taken on a Nicolet NT-300 instrument. Chemical shifts are
`
`in parts per million {o values) relative to tetramethylsilane (TMS) or sodium
`
`2,2·dimethyl-2·silapentane-5-sulfonate (DSS) and coupling constants (J
`
`
`
`110
`
`values) are in Hertz. Mass spectra were performed atthe Eli Lilly Corporation,
`
`Indianapolis, Indiana ,or by Dr. John Chinn at the Department of Chemistry,
`
`University of Texas at Austin. Elemental analysis was conducted at the Eli
`
`Lilly Corporation, Indianapolis,
`
`Indiana. Furan (ZQa), pyrrole (ll), ethyl
`
`chloroformate, isobutyl chloroformate, benzylamine (a.3.). methanesulfonic
`
`acid, boron trifluoride etherate, benzo[b]thiophene (.Z.!i), indole (12) and
`
`triethylamine were purchased from Aldrich Chemical Company, Milwaukee,
`
`Wisconsin; ethyl acetamidocyanoacetate and NaBH4 were obtained from
`
`Sigma Chemical Company, SL Louis, Missouri; . benzofuran (25.) was
`
`obtained from Chemicals Procurement Laboratories Inc., College Point, New
`
`York; and benzothienylglycine (Z3.ll.) was provided by Eli Lilly Corporation,
`
`Indianapolis, Indiana. Acetonitrile and triethylamine were distilled from CaH2
`and tetrahydrofuran and ethyl ether were distilled from Na/benzophenone.
`
`Furan (I.Q..a), pyrrole (ZA.). benzofuran (li). acetic anhydride (.!&). ethyl
`
`chloroformate, isobutyl chloroformate and methanesulfonic acid were
`
`fractionally distilled prior to use. All other chemicals were of the highest
`
`grade available and were used without further purification. The mixed
`
`anhydride reactions and the amidoalkylation transformations using boron
`
`trifluoride etherate were run under anhydrous conditions. In these cases, all
`
`glassware was flame-dried under N2, the solid starting materials were dried
`in yacuo immediately prior to use, and the reactions were conducted under a
`
`positive pressure of N2. Preparative flash column chromatography was run
`using Merck silica gel, grade 60, 230-240 mesh, 60 A from Aldrich Chemical
`
`Company, Milwaukee, Wisconsin.
`
`
`
`111
`
`Method A.
`
`Preparation of Methyl 2-Acetamldo-2-methoxyacetate
`
`(llllli}. Sulfuric acid (95%, 4 ml, 70 mmol} was added to a methanolic
`
`solution (230 ml) of 2-acetamido-2-hydroxyacetic acid (Ia) (13.30 g, 100
`
`mmol}. The solution was stirred at room temperature (48 h}, neutralized with
`solid NaHC03, filtered, and then the methanol was removed in vacuo. The.
`pink oil was distilled under vacuum (70-120 °C, 0.6 torr) to give a colorless oil
`
`which was recrystallized from petroleum ether (35-60 °C) to yield 5.20 g
`
`(32%) of the desired product: R1 0.52 (98:2 chloroform/methanol): mp 44-46
`°C; 1H NMR (300 MHz, CDCl3) o 2.08 (s, CH3CO), 3.46 (s, OCH3), 3.81 (s,
`COOCH3). 5,54 (d, J = 9.3 Hz, CH), 6.70-6.80 (br d, NH); 13c NMR (75
`
`MHz, CDCl3) 22.98 (CH3CO). 52.69 (COOCH3), 56.48 (CH30), 78.16
`
`(CH), 168.49 (CH3CO). 170.67 (COOCH3) ppm; IR (KBr) 3270, 2820, 1735,
`1650 (br), 1505, 1205, 1110, 1090, 1010, 930, 900 cm·1; mass spectrum, m/e
`
`(relative intensity) 162 (1 ), 146 (2), 131 (3), 118 (3). 102 (46), 88 (25), 60
`
`(100).
`
`Anal. Calcd for C6H11N04: C, 44.72; H, 6.88; N, 8.69. Found: C,
`
`44.46; H, 7.14; N, 8.72.
`
`Preparation of Ethyl 2-Acetamldo·2-ethoxyacetate (fil!.12).
`
`Sulfuric acid (95%, 4 ml, 70 mmol) was added to an ethanolic .solution (250
`
`ml) of 2-acetamido-2-hydroxyacetic acid (Zil.) (13.30 g, 100 mmol). The
`
`solution was stirred at room temperature (48 h) and then poured into a chilled
`
`saturated aqueous solution of NaHC03 (250 ml) and extracted with ethyl
`acetate (3 x 100 ml). The organic layers were combined, dried (MgS04) and
`
`
`
`112
`
`evaporated to dryness in vacuo. The oily residue was purified by distillation
`
`under vacuum (70-95 °C, 0.3-0.8 torr) to give 10.52 g (55%) of a white waxy
`
`solid: Rt 0.53 (98:2 chloroform/methanol): mp 35-36 °C; 1 H NMR (300 MHz,
`CDCl3) o 1.23 (t, J = 7,3 Hz, OCH2CH3), 1.32 (t, J = 7.3 Hz, OCH2CH3), 2.08
`(s, CH3CO), 3.70 (q, J = 7.3 Hz, OCH2CH3), 4.25 (q, J = 7.3 Hz,
`COOCH2CH3), 5.60 (d, J = 9.6 Hz, CH), 6.96 (br d, J = 9.6 Hz, NH) ; 13c
`NMR (75 MHz, CDCl3) 13.78 (OCH2CH3), 14.75 (OCH2CH3), 22.91
`
`(CH3CO), 61.74 (COOCH2CH3), 64.72 (OCH2CH3), 76.85 (CH), 168.25
`
`(CH3CO), 170.48 (COOCH2CH3) ppm; IA (KBr) 3400 (br), 1735, 1655 (br),
`
`1200, 1085 (br), 1010, 930, 890 cm·1; mass spectrum, m/e (relative intensity)
`
`190 (5), 160 (2), 144 (38), 116 (98), 102 (92), 74 (100); high resolution mass
`spectrum, calcd for c8H15N04 190.1079, found 190:1087.
`
`Preparation of Alkyl 2-Substituted-2-acetamidoacetates
`
`fil).General Procedure.The alkyl 2-acetamido-2-alkoxyacetate (fill) (1
`
`equiv) was suspended in anhydrous ethyl ether (60 mU10 mmol), and then
`
`boron trifluoride etherate (1.6 equiv) was added in one portion followed by
`
`the heterocycle (4 equiv). The solution was stirred at room temperature (72 h)
`
`and then poured into an ice-cold saturated aqueous solution (50 ml) of
`
`NaHC03, stirred at ice temperature (20 min), and then extracted with ethyl
`acetate (3 x 40 ml). The organic layers were combined, dried (Na2so4),
`and concentrated to dryness in vacuo. The resulting oil was purified by flash
`
`chromatography or recrystallization.
`
`Preparation of Methyl o:-Acetamldo-2-furanacetate (SJ.JD.
`
`The preceeding procedure was employed using methyl 2-acetamido-2-
`
`
`
`113
`
`methoxyacetate (fill.a) (1-68 g, 10.4 mmol), boron trifluoride etherate (2.71 g,
`
`2.35 ml, 16.6 mmol) and furan CZQil) (2.81 g, 3 ml, 41.6 mmol) to produce a
`
`black oil which was purified by flash chromatography
`
`(99:1 chloroform/
`
`methanol) to give1.28 g (62%} of the desired product as a beige solid: Rt
`
`0.32 (99:1 chloroform/methanol); mp 80-81 °C; 1H NMR (300 MHz, CDCl3} l>
`2.03 (s, CH3CO), 3.75 (s, COOCH3), 5.77 (d, J = 7.8 Hz, CH), 6.35-6.36 (m,
`C3>H, C4·H), 7.02 (d, J = 7.8 Hz, NH}, 7.36 (br s, c5.H); 13c NMR (75 MHz,
`CDCl3) 22.69 (CH3CO), 50.43 (COOCH3), 52,88 (CH), 108.72 (C3•),110.78
`
`(C4o), 142.84 (C5•), 148.89 (C2·). 169.57 (CH3CO}, 169.96 (COOCH2CH3)
`
`ppm; JR (KBr} 3200, 1740, 1620 (br), 1530 (br), 1205, 1090, 1020, 900, 890
`
`cm-1; mass spectrum, m/e (relative intensity) 197 (14), 165 (35), 154 (78),
`
`138 (36), 96 (100}, 94 (93}, 69 (16).
`
`Anal. Calcd for C9H11 N04: C, 54.82; H, 5.62; N, 7.10. Found: C,
`
`54.96; H, 5.40; N, 7.27.
`
`Preparation of Ethyl a·Acetarnldo-2-furanacetate (lt!.Q).
`
`The preceeding procedure was employed using ethyl 2-acetamido-2-
`
`ethoxyacetate (l.l.ll.12) (3.72 g, 19.7 mmol}, boron trifluoride etherate (3.75 g,
`
`3.25 ml, 26.4 mmol) and furan (1.Qg) (5.35 g, 5.70 ml, 78.6 mmol) to produce
`
`a black oil which was purified by two successive flash chromatographies ((a)
`
`100% chloroform, (b) 70:30 ethyl ether/pentane ,then 97:3 chloroform/
`
`methanol) to give 2.11 g (51 %) of the desired product as a white solid: R1
`0.17 (100% chloroform); mp 69-70 °C; 1H NMR (300 MHz, CDCl3) l> 1.24 (t, J
`
`= 7.2 Hz, COOCH2CH3). 2.04 (s, CH3CO), 4.14 - 4.32 (m, COOCHzCH3).
`5.75 (d, J = 8.1 Hz, CH), 6.34-6.35 (m, C3°H, C4•H), 6.35-6.54 (br d, J = 8.1
`
`Hz, NH), 7.35-7.36 (m, c 5 °H); 13c NMR (75 MHz, CDCl3 ) 13.91
`
`
`
`114
`
`(COOCH2CH3), 22.81 (CH3CO), 50.33 (CH), 62.08 (COOCH2CH3), 108.49
`
`(C3•), 110.62 (C4•), 142.64 (C5•). 148.85 (C2•), 168.89 (CH3CO), 169.43
`
`(COOCH2CH 3) ppm; IR (KBr) 3200, 1750, 1635 (br), 1530, 1380, 1335,
`1205, 1180, 1020, 890, 745, 595 cm-1 ;mass spectrum,m/e(relative intensity)
`
`211 (8),168 (32), 138 (27), 96 (100), 94 (27).
`
`Anal. Calcd for C10H13N04: C, 56.87; H, 6.20; N, 6.63. Found: C,.
`
`56.98; H, 6.19; N, 6.83.
`
`Preparation of Ethyl a·Ace.tamldo-2-pyrroleacetate
`
`(.!UJU
`
`and a·Acetamido-3-pyrroleacetate (~ .The preceeding procedure
`
`was employed using ethyl 2-acetamido-2-ethoxyacetate (fillll) (3. 78 g, 20
`
`mmol), boron trifluoride etherate (4.53 g, 4.84 ml, 32 mmol) and pyrrole (11)
`
`(5.36 g, 5.54 ml, 80 mmol) to produce a black oil. TLC analysis indicated the
`
`presence of
`
`two major compounds (Rt 0.33 and Rt 0.19, 98:2
`
`chloroform/methanol) which were isolated by flash chromatography (98:2
`
`chloroform/ methanol).
`
`The initial fraction (Rf 0.33, 98:2 chloroform/methanol) was further
`
`purified by another flash chromatography (97:3 dichloromethane/metha-
`
`nol) to produce 1.74 g (41%) of the desired product as a light brown solid: mp
`104-106 °C; 1 H NMR (300 MHz, DMSO-d6) o 1.16 (t, J =7.2 Hz, CH2CH3),
`1.88 (s, CH3CO), 4.01-4.16 (m, CH2CH3), 5.33 (d, J = 6.9 Hz, CH), 5.96-5.99
`(m, C3•H, C4•H), 6.69-6.72 (m, C5•H), .8.48 (d, J =6.9 Hz, CONH).
`
`10.80-10.99 (br S, NH); 13c NMR (75 MHz, CDCl3) 13.93 (CH2CH3) 22.79
`
`(CH3CO), 50.73 (CH), 61.38 (CH2CH3), 106.35 (C3•), 107.52 (C4•), 118.07
`
`(C5•), 125.28 (C2•), 169.24 (CH3CO), 170.11 (COOCH2CH3) ppm; IR (KBr)
`
`3310, 3200, 1715, 1635 (br), 1515 (br), 1220, 1180, 1085, 1010, 890 crn-1;
`
`
`
`115
`
`mass spectrum, m/e (relative intensity) 210 (22), 167 (36), 137 (54), 121 (7),
`
`106 (7), 95 (100), 93 (97), 79 (5), 68 (53).
`
`Anal. Calcd for C10H14N203: C, 57.13; H, 6. 71; N, 13.33. Found: C,
`
`57.20; H, 6.55; N, 13.13.
`
`The second fraction (Rf 0.19, 98:2 chloroform/methanol) was further
`
`purified by a second flash chromatography (95:5 dichloromethane/
`
`methanol) to give 0.52 g (12%) of the desired product as a beige solid: mp
`
`92-93 °C; 1 H NMR (300MHz, CDCl3) l> 1.25 (t, J =6.9 Hz, CH2CH3), 2.02 (s,
`
`CH3CO), 4.10-4.30 (m, CH2CH3 ), 5.53 (d, J =7.2 Hz, CH), 6.17-6.30 (m.
`C4•H), 6.25 (d, J = 7.2 Hz, CONH), 6.70-6.75 (m. C5·H), 6.78-6.80 (m, C2·H),
`8.45-8.60 (brs, NH); 13c NMR (75 MHz, CDCl3). 13.93 (CH2CH3). 22.79
`
`(CH3CO), 50.73 (CH), 61.38 (CH2CH3). 106.78 (C4•). 116.56 (C2·). 118.25
`
`(C3-}, 118.63 (C5•), 169.79 (COCH3), 171.76
`
`(COOCH2CH3) ppm; IR (kBr)
`
`3320, 3240, 1720, 1640 (br), 1510, 1400 (br), 1210, 1180, 1010, 890 cm-1;
`
`mass spectrum, m/e (relative intensity) 210 (12), 167 (16), 152 (5), 137 (31),
`
`121 (3), 95 (100), 93 (100), 80 (5), 68 (71 ); high resolution mass spectrum,
`
`calcd for C10H14N203 210.1004, found 210.1015.
`
`Preparation of 2-Substltuted 2-Acetamldoacetlc Acids
`(ll). Preparation of a.-Acetamldo-2-furanacetlc Acid (!:!2fil. Ethyl
`
`a.-acetamido-2-furanacetate (fill2) (2.93 g, 13.8 mmol) was dissolved in 90:10
`
`ethanol/water (11 O ml), and KOH (0.85 g, 15.2 mmol) was added and the
`
`solution was stirred at room temperature (48 h). The solution was
`
`concentrated in vacuo and the residue diluted with H20 (100 ml) and then
`
`extracted with ethyl acetate (3 x 100 ml). The aqueous layer was then
`
`acidified with 8.5% H3P04 (25 ml) and extracted with ethyl acetate (3 x 200
`
`
`
`116
`
`ml). The organic layers were combined, dried (Na2so 4) and then
`evaporated to dryness in yacyo to produce a beige solid (2.00 g) which was
`
`recrystallized (acetonitrile) to yield 1.31 g (51%) of the desired product as
`
`beige crystals: Rf 0.37 (8:1 :1 isopropanol/NH40HIH20); mp 171-172 °C; 1H
`NMR (300 MHz, DMSO~d6) o 1.88 (s, CH3), 5.45 (d, J = 7.8 Hz, CH),
`6.39-6.45 (m, C3•H, C4·H), 7.65 (s, C5·H), 8.69 (d, J = 7.8 Hz, NH). [The
`carboxyl proton was not detected.]. 13c NMR (75 MHz, DMSO- d6) 22.10
`(CH3), 50.16 {CH), 108.17 (C3•), 110.66 (C4•), 142.83 (C5>), 149.75 (C2-)
`
`169.21 {CH3CO), 170.01 (COOH) ppm; IR (KBr) 3320, 3100, 1705, 1580 (br).
`
`1530, 1410, 1360, 1320, 1280, 1270, 1225, 1210, 1145, 1100, 1010, 890,
`
`640, 660, 610, 570, 400 cm-1; mass spectrum, m/e {relative intensity) 183
`
`(2), 165 (10), 140 (24), 123 (19), 109 (1), 96 (100), 94 (43), 80 (2), 69 (8).
`
`Anal. Calcd for c 8H9No4: C, 52.46; H, 4.95; N, 7.65. Found: C,
`52.61; H, 4.93; N, 7.94.
`
`Preparation of a-Acetamldo-2-pyrroleacetic Acid
`
`(!l£QJ.
`
`Ethyl a-acetamido-2-pyrroleacetate (JilQ) (2.11 g, 1 O mmol) was dissolved in
`
`90:1 O ethanol/water (88 ml), and then KOH (0.61 g, 11 mmol) was added
`
`and the resulting solution stirred at room temperature (48 h). The solution
`
`was concentrated in vacuo and the residue diluted with H20 (80 ml) and
`
`washed with ethyl ether (3 x 80 ml). The aqueous layer was then made
`
`acidic with 8.5% H3Po4 (20 ml) and extracted with ethyl acetate (3 x 100
`ml). The organic layers were combined, dried (Na2S04) and evaporated in
`vacuo to give a brown solid which was successively triturated with ethyl
`
`acetate (50ml) and petroleum ether (35-60 °C) (650 ml), and then
`
`recrystallized (chloroform/methanol/ hexanes) to give 0.53 g (29%) of the
`
`
`
`117
`
`desired product as beige crystals: Rt 0.55. (8:1 :1 isopropanoVNH40H/H20);
`mp 112-114 °C; 1 H NMR (300 MHz, DMSO-d5) S 1.87 (CH3), 5.31 (d, J = 7.2
`
`Hz, CH), 5.96 (s, C3•H), 5.97 (s, C4•H), 6.87 (s, C5•H), 8.40 (d, J = 7.2 Hz,
`
`CONH), 10.79-10.85 (br s, NH). [rhe carboxyl proton was not detected.]. 13c
`
`NMR (75 MHz, DMSO-d5) 22.16 (CH3), 50.45 (CH), 106.21 (C3•), 107.45
`
`(C4•), 117.83 (C5•), 126.11(C2•),169.13 (CH3CO), 171.56 (COOH) ppm; IR
`
`(KBr} 3340, 3300,1710, 1590 (br), 1530 (br), 1220, 1080, 885, 725 cm·1 ;mass
`
`spectrum, m/e (relative intensity)182 (1), 164 (7), 151 (45), 138 (100). 137
`
`(25), 121 (2), 95 (98), 93 (10), 91 (46).
`
`Preparation of a-Acetamldo-3-pyrroleacetlc Acid (.!l.2fil,
`
`Ethyl a-acetamido-3-pyrroleacetate (fil.d) (0.81 g, 3.85 mmol) was dissolved
`
`in 90:10 ethanol/water (33 ml), and then KOH (0.24 g, 4.2 mmol) was added
`
`and .the resulting solution stirred at room temperature (48 h). The solution
`
`was concentrated in vacuo and the residue diluted with water (30 ml), and
`
`then washed with ethyl ether (3 x 30 ml). The aqueous layer was then made
`
`acidic with 8.5% H3P04 (8 ml) and extracted with ethyl acetate (4 x 30 ml).
`The organic layers were combined, dried (Na2S04) and evaporated in
`
`vacuo,
`
`The
`
`resulting beige
`
`solid was
`
`recrystallized
`
`(chloroform/methanol/hexanes) to give 0.27 g (38%) of the desired product
`
`as beige crystals: R1 0.28 (8:1:1 isopropanol/NH40HIH20); mp 135-138 °C;
`
`1 H NMR (300 MHz, DMSO-d6) I) 1.85 (s, CH3), 5.05 (d, J = 7.0 Hz, CH), 6.04
`(s, C4•H), 6.69 (s, C2•H), 6.76 (s, C5•t1). 8.23 (d,.J = 7.0 Hz, CONH),
`10.68-10.86 (br s, NH). [the carboxyl proton was not detected). 13c NMR (75
`
`MHz, DMSO-d5) 22.18 (CH3), 50.57 (CH), 106.98 (C4•), 116.28 (Cz•),
`
`- - - - - - - - -
`
`
`
`1 18
`
`117.83 (C3• and C5•), 169.13 (CH3CO), 173.00 (COOH) ppm; IA (KBr) 3340,
`
`3300, 1700, 1585 (br), 1525 (br), 1240 (br), 920, 895 cm-1; mass spectrum,
`
`m/e (relative intensity) 182 (4), 164 (6), 157 (1), 138 (100), 124 (3), 121 (38),
`
`95 (19), 93 (33), 80 (94), 68 (91 ); high resolution mass spectrum, calcd for
`
`C8H10N203 182.0691, found 182.0688.
`
`Preparation of a-Acetamldo-2-benzofuranacetlc Acid
`(f!..2.!!).2-Acetamido-2-hydroxyacetic acid CZ.a) (6.65 g, 50 mmol) was
`dissolved in glacial acetic acid (12 ml) and the resulting yellow solution was
`
`chilled in an ice bath, benzofuran (15.) (11.80 g, 11 ml, 100 mmol) was then
`
`added in one portion, followed by the rapid dropwise addition of
`
`methanesulfonic acid. The orange solution was stirred at room temperature
`
`(16 h) and the solution was poured into an ice-water mixture (100 ml) and
`
`then triturated. The resulting semi-solid was separated from the aqueous
`
`layer and recrystallized from petroleum ether {35-60 °C) and then triturated
`
`with ethyl acetate. The product was further purified by recrystallization
`
`(acetonitrile) and then dissolved in a 5% aqueous NaOH solution, washed
`
`with ethyl acetate, and then made acidic (pH 1) with 10% aqueous HCI and
`
`filtered to give 2.38 g (20%) of the desired product as white crystals: Rf 0.62
`(8:1:1 isopropanol/NH40H/H20); mp 203·204 °C; 1H NMR (300 MHz,
`
`DMSO-d6) Ii 1.91 (s, CH3), 5.66 (d, J = 7.8 Hz, CH), 6.90 (s, C3'H), 7.23-7.35
`(m, C5•H, C5·H), 7 .. 55-7.65 (m, C4°H, C7°H), 8.85 (d, J = 7.8 Hz, NH). [The
`carboxyl proton was not detected]. 13c NMR (75 MHz, DMSO-d6) 22.11
`(CH3), 50.51 (CH), 104.93 (C3•), 111.06 (C?'), 121.22 (C4•), 123.02 (C5•).
`
`124.51 (C5•), 127.65 (C3·8 ), 152.92 (C7'8 ), 154.10 (C:z·), 169.20 (COCH3).
`
`
`
`119
`
`169.62 (COOH) ppm; IR (kBr) 3340, 3090, 1720, 1590 (br), 1535 (br), 1240,
`
`1200, 1090, 890, 750 cm-1; mass spectrum, m/a (relative intensity) 233 (12),
`
`. 215 (2), 190 (38), 173 (15), 146 (100), 144 (92), 130 (14), 91 (32).
`
`Anal. Calcd for C12H11N04: C, 61.80; H, 4.75; N, 6.01. Found: C,
`
`61.55; H, 4.76; N, 5.77.
`
`Preparation of a.-Acetam ldo-2-benzo [b ]thlophenea cetlc
`Acid (l!Zru. a.-Amino-2-benzo[b]thiopheneacetic acid (Uf.) (5.18 g, 25
`
`mmol) was suspended in H20 (60 ml), and then NaOH (1.50 g, 37 mmol)
`
`was added and the suspension stirred until a homogeneous solution was
`
`obtained. The aqueous solution was cooled to 5 °C, and then acetic
`
`anhydride (.fili) (5.08 g, 4.70 ml, 50 mmol) was added slowly so as to
`
`maintain the temperature of the solution below 7 °C. The solution was stirred
`
`an additional 5 min and then an aqueous NaOH (2.50 g, 63 mmol) solution
`
`(15 ml) was added and the solution stirred 30 min. The reaction was then
`
`f:
`l~--
`
`made acidic (pH 1) with 10% aqueous HCI and the resulting precipitate (5.93
`
`g) was filtered and washed with H20 (2 x 15 ml). The beige crystals were
`
`dissolved in an aqueous NaOH (1.00 g, 25 mmol) solution (100 ml) and the
`
`solution was extracted with ethyl acetate (2 x 50 ml) and then the aqueous
`
`solution was made acidic with 10% aqueous HCI. The precipitate which
`
`formed was washed with H20 to yield 5.23 g (83%) of the desired product as
`beige crystals: mp 224-226 °C; iH NMR (300 MHz, NaOD/020) o 2.08 (s,
`CH3 ), 7.36-7.45 (m, C3·H, C5'H, C7'H), 7.81· 7.84 (m, C4•H or C5·H)
`7.88-7.92 (m, C4'H or Cs·H) ppm. [rhe a-proton was not observed in the
`employed NMR solvent and is presumed to have undergone C-H to C-D
`
`exchange.]. 13c NMR (75 MHz, NaODID20) 26.33 (CH3).59.85 (t, CH),
`
`
`
`120
`
`126.86 (C4• or Cr). 127.18 (C4• or CrJ. 128.12 (C3•), 129.08 (Cs• or
`C5•), 129.09 (C5• or C5•), 143.66 (C3•a or Cy•8 ). 143.71 (C3•8 or Cr8 ),
`146.03 (C2·); IR (KBr) 3305, 1710, 1580 (br), 1525 (br), 1275, 1200, 1090,
`
`890cm·1; mass spectrum, m/e (relative intensity) 249 (22), 231 (20),206 (33),
`
`189 (6), 162 (100),160 (89), 135 (38), 89 (26).
`
`Anal. Calcd for C12H11N03S: C, 57.82; H, 4.45; N, 5.62. Found:
`
`C, 57.55; H, 4.38; N, 5.35.
`
`Pre para ti on of 2-Subs tituted-2-acetamldo-N.-be nzyl-ace(cid:173)
`tamides (fil!. w. Preparation of o:-Acetamido-N.-benzyl-2-fura(cid:173)
`acetamide (fill.l!.). o:-Acetamido-2-furanacetic acid (fl..2..a) (0.47 g, 2.56
`
`rnmol) was combined with acetonitrile (10 ml) and cooled to -5 °C (ice/salt
`
`water bath). Triethylamine (0.26 g, 0.36 ml, 2.56 mmol) was then rapidly
`
`added and the mixture stirred at -5 °c (3 min). Ethyl chloroformate (0.28 g,
`
`0.25 ml, 2.56 mmol) was added dropwise between -4 and -3 °C, and the
`
`resulting suspension was stirred at -4 °C (20 min). and then an acetonitrile
`
`solution (2 ml) of benzylamine (.!U) (0.30 g, 0.31 ml, 2.82 mmol) was
`
`carefully added. During the addition of benzylamine the temperature of the
`
`solution did not go above O °C. The mixture was stirred at -5 °C (1 h) and at
`room temperature (18 h), and then concentrated in vacuo. The residue was
`
`then triturated with hot tetrahydrofuran (5 ml), cooled at -16 °C (3 h), and the
`
`resulting white precipitate was filtered and identified as triethylamine
`hydrochloride (1 H NMR (60 MHz, DMSO-d6) o 1.00 (t, J = 7.5 Hz, CH3), 2.82
`(q, J,;, 7.5 Hz, CH2), 3.83 (s, NH)) 164. The filtrate was evaporated to dryness
`in vacuo and the resulting oil purified by flash chromatography (98:2
`
`
`
`121
`
`chloroform/ methanol) to give 0.09. g (13%) of the desired product as a white
`
`solid: Rt 0.30 (98:2 chloroform/methanol); mp 178-179 °C; 1 H NMR (300
`MHz, DMSO-d5) o 1.90 (s, CH3), 4.31 (d, J = 6.0 Hz, CH2). 5.58 (d, J = 8.1
`Hz, CH), 6.27-6.33 (m, C3·H), 6.40-6.44 (m, C4•H), 7.20-7.36 (m, Ph),
`. .
`. 13
`7.60-7.64 (m, C5·H), 8.58 (d, J = 8.1 Hz, NH), 8.73 (t, J = 6.0 Hz, NH), C
`NMR (75 MHz, DMSO-d5) 22.35 (CH3), 42.27 (CH2). 50.95 (CH), 107.60
`
`(C3•), 110.55 (C4•), 126.82 (2C2" or 2C3"), 127.08 (2C2" or 2C3u),
`
`128.27 (C4"), 139.05 (C1"), 142.58 (C5•), 151.16 (C2•), 168.02 (CH3CO),
`
`169.30 (NHCO) ppm; IR (KBr) 3230, 1625 (br), 1525 (br), 1375 (br), 1230,
`1090, 890, 740, 690 cm·1; mass spectrum, m/ e (relative intensity) 273 (1 ),
`
`230 (1 ), 139 (100), 96 (94), 91 (51 ), 65 (9).
`
`Anal. Calcd for C15H1sN203: C, 66.16; H, 5.83; N, 10.29. Found:
`
`C, 65.92; H, 5.83; N, 10.15.
`
`Preparation of u·Acetamldo-li-benzyl-2-benzofuranacet(cid:173)
`
`amide(.6.fil).u-Acetamido-2-benzofuranacetic acid (.82..d) (2.38 g, 10.2 mmol)
`
`was combined with acetonitrile (100 ml) and then triethylamine (1.01 g, 1.39
`
`ml, 10.2 mmol) was added. The mixture was stirred at room temperature (20
`
`min) and then cooled to -5 °C (ice/salt water bath) and isobutyl chloroformate
`
`(1.37 g, 1.30 ml, 10.2 mmol) was added rapidly. The mixture was stirred
`
`between -5 and -8 °C (20 min) and then an acetonitrile solution (5 ml) of
`
`benzylamine (.8.:2) (1.18 g, 1.19 ml, 11.0 mmol) was added dropwise. The
`
`resulting suspension was stirred at -5 °C (1 h) and at room temperature (17
`h). The mixture was then concentrµted in yacuo and the yellowish residue
`
`triturated with tetrahydrofuran (150 ml) and cooled at -16 °C (4 h). The
`
`resulting precipitate was filtered and identified as triethylamine hydrochloride
`
`
`
`122
`
`(1 H NMR ( 60 MHz, DMSO-d5) S 1.00 (t, J = 7.5 Hz, CH3), 2.82 (q, J 7.5 Hz,
`CH2). 3.83 (s, NH}) 164. The remaining filtrate was concentrated to (- 5 ml)
`in vacuo and refrigerated (-16 °C) resulting in the formation of a precipitate
`
`which was
`
`filtered and purified by
`
`flash chromatography
`
`(98:2
`
`chloroform/methanol) to give 0.42 g (13%) of the desired product as a white
`solid: Rf 0.30 (98:2 chloroform/methanol); mp 195-196 •c; 1H NMR (300
`MHz; DMS0-06) S 1.94 (s, CH3), 4.34 (d, J = 5. 7 Hz, CH2), 5. 77 (d, J = 8.1
`Hz. CH), 7.24-7.32 (m, C3°H, C5°H, C5•H, Ph), 7.54 (d, ../ = 7.0 Hz. C4·H or
`CTH), 7.62 (d, J = 7.0 Hz, C4'H or. C7'H), 8.74 (d, J = 8.1 ·Hz, NH), 8.86 (t, J =
`5.7 Hz, NH); i 3c NMR (75 MHz, DMSO-d5) 22.27 (CH3), 42.30 (CH2).
`
`51.22 (CH),