Synthesis of the isonicotinoylnicotinamide scaffolds of the naturally occurring isoniazid-NAD(P) adducts

Article abstract of DOI:10.1021/jo062100e

The first syntheses of the 1-hydroxy-1-(pyridin-4-yl)-1,2-dihydro-3H- pyrrolo[3,4-c]pyridin-3-one heterocycle and the 3-aminocarbonyl-4-isonicotinoyl- 1,4-dihydropyridine framework present in the isoniazid-NAD(P) adducts are described.

Full text of DOI:10.1021/jo062100e

Synthesis of the Isonicotinoylnicotinamide
Scaffolds of the Naturally Occurring
Isoniazid-NAD(P) Adducts
able to inhibit the dihydrofolate reductase (DHFR) of Mtb
5
(Scheme 1). Moreover, Tonge and collaborators described that
the benzoylhydrazine-NAD adduct (BH-NAD) formed from
the reaction of the activated benzoic acid hydrazide and NAD
6
is also an inhibitor of InhA (Scheme 1).
Tamara Delaine, Vania Bernardes-G e´ nisson,
Thus, the great interest revealed by this category of biologi-
cally relevant molecules prompted us to investigate the pos-
sibilities for synthesis of the benzoyl- and isonicotinoylnicoti-
namide scaffolds. Recently, we have published the first chemical
synthesis of 4-benzoylnicotinamide (1), the core structure of
the BH-NAD adduct (Scheme 2). In fact, this compound exists
§
Bernard Meunier, and Jean Bernadou*
Laboratoire de Chimie de Coordination du CNRS, 205 route de
Narbonne, 31077 Toulouse cedex 4, France
bernadou@lcc-toulouse.fr
7,8
exclusively under the ring hemiamidal form 2. No equilibrium
between the ring (hemiamidal) and the chain (ketoamide)
structure was observed. Further N-alkylation of 2 gave the
pyridinium compound 3, which could be regioselectively
reduced to afford the 4-benzoyl-1,4-dihydronicotinamide deriva-
ReceiVed October 10, 2006
7
,8
tive 4 (two epimers). This good synthetic result encouraged
us to prepare the unprecedented 4-isonicotinoylnicotinamide (5)
and the 4-isonicotinoyl-1,4-dihydronicotinamide frameworks
present in the naturally occurring INH-NAD(P) adducts 6/7
(Scheme 3). These compounds can be seen as potential
pharmacophores for designing new antibiotic drugs. It is
noteworthy that, despite the apparent simplicity of the 4-isoni-
cotinoylnicotinamide, this molecule is still unknown in the
literature. Moreover, synthesis and characterization of the
4-isonicotinoyl-1,4-dihydronicotinamide framework can be ex-
pected to be more complex than in the case of BH-NAD(P)
analogues since the 4-benzoyl-1,4-dihydronicotinamide exists
in only the chain ketoamide form (two epimers; Scheme 2),
whereas the INH-NAD adduct exists, in solution, as a mixture
The first syntheses of the 1-hydroxy-1-(pyridin-4-yl)-1,2-
dihydro-3H-pyrrolo[3,4-c]pyridin-3-one heterocycle and the
3-aminocarbonyl-4-isonicotinoyl-1,4-dihydropyridine frame-
work present in the isoniazid-NAD(P) adducts are described.
Tuberculosis (TB), a chronic disease caused by Mycobacte-
rium tuberculosis (Mtb), is one of the leading causes of death
from infectious origin in the world. The biggest threat is multi-
drug-resistant TB caused by strains resistant to at least isoniazid
of chain and ring tautomers, giving a total of six isomers (two
epimers for 6 and four stereoisomers for 7; Scheme 3).9
The 4-isonicotinoyl-1,4-dihydronicotinamide framework present
in INH-NAD(P) adducts (6/7) can theoretically be obtained
by following the same strategy as that for the preparation of
compound 4 (Scheme 2); a chemoselective alkylation of the
pyridinic nitrogen of nicotinamide in 5 followed by reduction
of the pyridinium intermediate would afford the desired 1,4-
dihydropyridine compound. Therefore, in a first step, various
methods were examined to prepare the 4-isonicotinoylnicoti-
namide compound 5. The approach using 4-pyridinyllithium
generated from 4-bromopyridine and BuLi to arylate 8 (Scheme
(
INH) and rifampicin. Although isoniazid is an old and simple
molecule used efficiently in the antitubercular therapy regimens,
its molecular mechanism of action is still a matter of debate.
The consensus opinion is that a Mtb catalase-peroxidase (KatG)
oxidizes INH, a prodrug, to an isonicotinoyl radical, which then
couples covalently to the NAD or NADP cofactor to give the
1
1
,4-dihydropyridine type adducts (Scheme 1). The resultant
INH-NAD and INH-NADP adducts (4S)-enantiomers were
found as strong inhibitors of InhA2 and MabA3 enzymes,
respectively, two key reductases involved in the biosynthesis
of mycolic acids, essential and specific constituents of the
mycobacteria envelope. Recently, Blanchard and co-workers
4) was unsuccessful, probably because of the difficult formation
4
and/or the instability of the 4-pyridinyllithium. Therefore, we
tried the same reaction using 3-bromopyridine, which is a
synthetic equivalent of 4-halopyridine, via subsequent removal
reported that the INH-NADP adduct (4R)-enantiomer is also
1
0
*
To whom correspondence may be addressed. Fax: 33 (0)5 61 55 30 03.
of the bromine atom (Scheme 4). The reaction provided a 1:3
Tel: 33 (0)5 61 33 31 17.
§
New address: Palumed, BP 28262, 31682 Lab e` ge cedex, France.
(
1) (a) Sinha, B. K. J. Biol. Chem. 1983, 258, 796-801. (b) Zhang, Y.;
Heym, B.; Allen, B.; Young, D.; Cole, S. Nature 1992, 358, 591-593.
2) (a) Rozwarski, D. A.; Grant, G. A.; Barton, D. H. R.; Jacobs, W. R.,
(5) Argyrou, A.; Vetting, M. W.; Aladegbami, B.; Blanchard, J. S. Nat.
Struct. Mol. Biol. 2006, 13, 408-413.
(
(6) Rawat, R.; Whitty, A.; Tonge, P. J. Proc. Natl. Acad. Sci. U.S.A.
2003, 100, 13881-13886.
Jr.; Sacchettini, J. C. Science 1998, 279, 98-102. (b) Wilming, M.;
Johnsson, K. Angew. Chem., Int. Ed. 1999, 38, 2588-2590. (c) Lei, B.;
Wei, C.-J.; Tu, S.-C. J. Biol. Chem. 2000, 275, 2520-2526. (d) Nguyen,
M.; Qu e´ mard, A.; Broussy, S.; Bernadou, J.; Meunier, B. Antimicrob. Agents
Chemother. 2002, 46, 2137-2143.
(7) Broussy, S.; Bernardes-G e´ nisson, V.; Qu e´ mard, A.; Meunier, B.;
Bernadou, J. J. Org. Chem. 2005, 70, 10502-10510.
(8) Broussy, S.; Bernardes-G e´ nisson, V.; Gornitzka, H.; Bernadou, J.;
Meunier, B. Org. Biomol. Chem. 2005, 3, 666-669.
(9) (a) Nguyen, M.; Claparols, C.; Bernadou, J.; Meunier, B. ChemBio-
Chem 2001, 2, 877-883. (b) Broussy, S.; Coppel, Y.; Nguyen, M.;
Bernadou, J.; Meunier, B. Chem.sEur. J. 2003, 9, 2034-2038.
(10) Karig, G.; Spencer, J. A.; Gallagher, T. Org. Lett. 2001, 3, 835-
838.
(3) Ducasse-Cabanot, S.; Cohen-Gonsaud, M.; Marrakchi, H.; Nguyen,
M.; Zerbib, D.; Bernadou, J.; Daff e´ , M.; Labesse, G.; Qu e´ mard, A.
Antimicrob. Agents Chemother. 2004, 48, 242-249.
(4) Takayama, K.; Wang, L.; David, H. L. Antimicrob. Agents Chemother.
1
972, 2, 29-35.
1
0.1021/jo062100e CCC: $37.00 © 2007 American Chemical Society
Published on Web 12/22/2006
J. Org. Chem. 2007, 72, 675-678
675

SCHEME 1. Formation of INH- and BH-NAD(P) Adducts in Mycobacterium tuberculosis
(N,N-diethylisonicotinamide,12 isonicotinaldehyde, 4-cyanopy-
ridine, and isonicotinoyl chloride), but in all of the cases, the
experiences were disappointing. More satisfactory results were
obtained in experiments involving the Weinreb amide 12 as the
aroylation agent (Scheme 4). Treatment of 10 with LDA in ether
at -78 °C, followed by addition of 12, gave the condensed
product 13 in a 39% yield. Afterward, reduction of the
ketoamide 13 by NaBH4 afforded the alcohol-amide 14.
Successive treatments of 14 by formic acid, NH3/MeOH, aq
HCl/air, and SOCl2/aq NH3 (according to methodology de-
scribed in ref 8) successfully provided 5 in a 77% yield. The
overall yield for the conversion of 10 into 5 was 29%.
SCHEME 2.
Benzoylnicotinamide and Benzoyldihydro-
nicotinamide Scaffolds7,8
SCHEME 3. Isonicotinoylnicotinamide (Ring Tautomer)
and Isonicotinoyldihydronicotinamide Scaffolds
8
As shown previously for the corresponding phenyl derivative
2
(Scheme 2), compounds 9 and 5 were unambiguously
13
confirmed by C NMR (C7 at 85.4 and 86.3 ppm, respectively)
to exist only under a ring hemiamidal structure (azaisoindoli-
none), which might serve as a masked synthon of the ketoamide
moiety for further syntheses in the 1,4-dihydronicotinamide
series.
In a second part of this work, we tried to prepare the
isonicotinoyl-1,4-dihydronicotinamide scaffolds present in the
INH-NAD(P) adducts (Scheme 3) following the strategy
depicted in Scheme 2 for synthesis of BH-NAD analogues.
The N-alkylation of 5, carried out with ethyl bromoacetate, did
not lead to the expected compound 15 (through alkylation on
the nitrogen of the nicotinamide moiety, Scheme 4) but, in
contrast, took place preferentially on the pyridine ring to give
mixture of meta/para11 regioisomers in a 10% yield. The pure
para product 9 was obtained by recrystallization in acetone (5%
yield). The low efficiency of this reaction could be explained
by the significant amounts of 4-N,N-diisopropylaminopyridine
+
(
(
m/z 179 [M + 1]) and 4-(3-bromopyridinyl)-3-bromopyridine
+
m/z 315 [M + 1]) formed as byproducts. The subsequent
1
4 1
a monoalkylated derivative ( H NMR: δ H2 9.11, H6 8.82,
removal of the bromine atom of 9 by a metal-halogen exchange
reaction (BuLi) notably afforded, for the first time, the pyridinyl
derivative 5. However, the low yield for the preparation of the
intermediate 9 makes this approach not suitable to prepare the
isonicotinoylnicotinamide scaffold.
H5 7.57, H12 9.00, H11 8.34 ppm) along with a bisalkylated
1
5
derivative on both the pyridine and the nicotinamide rings
1
(
H NMR: δ H2 9.58, H6 9.27, H5 8.43, H12 9.09, H11 8.47
ppm). As a consequence of this unsuccessful synthetic route,
we turned our attention to the study of direct preparation of the
dihydropyridine derivatives 17/18 by a biomimetic approach.9
It serves to activate INH by a chemical procedure able to mimic
the mycobacterial catalase-peroxidase activity (KatG). It is
known that the catalase-peroxidase KatG can catalyze the
In order to find a more efficient synthetic strategy to 5, we
examined another methodology previously developed by us to
,13
8
prepare the phenyl analogue 2. This approach was based on a
direct ortho-metalation of N,N-diisopropylnicotinamide (10),
followed by a reaction with N,N-dimethylbenzamide as the
benzoylation agent. In the case of preparation of the pyridinyl
analogue 5, the N,N-dimethylisonicotinamide is not easily
available; therefore, we investigated other electrophilic agents
II
III
III
conversion of Mn into Mn and, then, that Mn , acting as a
(
13) Nguyen, M.; Claparols, C.; Bernadou, J.; Meunier, B. C. R. Acad.
Sci. 2001, 5, 1-6.
14) 1-[2-(Ethyloxy)-2-oxoethyl]-4-[1-hydroxy-3-oxo-1,2-dihydro-3H-
(
(
11) Meta and para refer to the position of the carbonyl group that
undergoes nucleophilic attack.
12) Watanabe, M.; Shinoda, E.; Shimizu, Y.; Furukawa, S.; Iwao, M.;
Kuraishi, T. Tetrahedron 1987, 43, 5281-5286.
pyrrolo[3,4-c]pyridin-1-yl]pyridin-1-ium bromide.
(15) 5-[2-(Ethyloxy)-2-oxoethyl]-1-[1-(2-(ethyloxy)-2-oxoethyl)pyridinium-
4-yl]-1-hydroxy-3-oxo-2,3-dihydro-1H-pyrrolo[3,4-c]pyridin-5-ium dibro-
mide.
(
6
76 J. Org. Chem., Vol. 72, No. 2, 2007

SCHEME 4. Synthesis of the Isonicotinoylnicotinamide Framework 5 from 3,4-Pyridinedicarboximide (8) and from
a
Diisopropylnicotinamide (10) using Weinreb Amide (12) as the Aroylation Agent
a
Reagents: (a) 3-Br-pyridine/LDA/THF; (b) BuLi/THF; (c) N,O-dimethylhydroxylaminehydrochloride/1-hydroxybenzotriazole/1-(3-dimethylaminopropyl)-
3
-ethylcarbodiimidehydrochloride/TEA/CH3CN; (d) LDA/ether; (e) NaBH4/ethanol; (f) (i) HCOOH, heat, (ii) NH3/MeOH, (iii) HCl, air oxidation, (iv)
SOCl2/NH3 aq/acetone; (g) BrCH2COOEt/THF.
SCHEME 5.
Synthesis of the Isonicotinoyldihydro-
tinoylnicotinamide). The most convenient one is based on an
ortho-metalation-electrophilic substitution sequence using a
Weinreb amide as the aroylation agent (overall yield from N,N-
diisopropylnicotinamide is 29%). Since the chemoselective
alkylation of the pyridinic nitrogen of the nicotinamide moiety
of 5 has not been possible, access to the 1,4-dihydronicotinamide
scaffold through a reduction step could not be envisioned by
this route. Therefore, the biomimetic approach, previously used
to prepare INH-NAD adducts, has been expanded to the
preparation of the truncated dihydropyridine analogues 17/18,
and this method presently represents the best way to prepare
the 4-isonicotinoyl-1,4-dihydronicotinamide framework. These
scaffolds are directly derived from the structure of the iso-
niazid-NAD(P) adducts that are considered as the biologically
relevant effectors of the antibiotic activity of isoniazid. The
synthesis of new potential inhibitors of Mtb reductases inspired
from these scaffolds is currently in progress in our laboratory.
a
nicotinamide Analogues 17/18 of the INH-NAD(P) Adducts
a
Reagents: (a) BrCH2COOEt/THF/heat; (b) Mn(H2P2O7)3/buffer.
mediator, can oxidize INH. Therefore, direct activation of INH
by a stoichiometric amount of manganese pyrophosphate (a
stable form of MnIII with a suitable redox potential in aqueous
solution) in the presence of the appropriate pyridinium salt 16
Experimental Section
(obtained, in turn, by reaction of nicotinamide with ethyl
bromoacetate, yield 87%) successfully afforded a 57% yield of
the targeted 1,4-dihydropyridines 17/18 (Scheme 5). The purity
of this equilibrated mixture was estimated to be about 90% by
HPLC analysis. Compounds 17/18 represent simplified ana-
logues of the naturally occurring INH-NAD(P) adducts, and
it is interesting to note that, as reported previously for these
1-Hydroxy-1-(pyridin-4-yl)-1,2-dihydro-3H-pyrrolo[3,4-c]py-
ridin-3-one (5), Prepared from 9. To a solution of 9 (93 mg, 3.0
mmol) in dry THF (6 mL), under argon at -78 °C, was added
butyllithium (0.6 mL, 1.5 M in cyclohexane, 9.1 mmol) dropwise,
and the mixture was allowed to warm to room temperature over 4
h. Water was added, and the solvent was evaporated under vacuum.
The crude was purified by silica gel column chromatography (CH
2
-
9
adducts, the 1,4-dihydropyridines 17/18 were found, in solution,
as an equilibrated mixture of ring (65-85%) and chain (15-
Cl /MeOH 95:5 to 90:10) to give a white powder (61 mg, 74%):
2
-1
mp 223-224 °C; IR (KBr, νmax/cm ) 3256, 3062, 1715, 1644,
3
5%) tautomers. Minor chain tautomer 18 was identified by its
1
1
8
6
606, 1536; H NMR (250 MHz, DMSO-d ) δ 9.65 (s br, 1H),
1
1
13
H NMR spectrum, while full description of the H and
C
.91 (s, 1H), 8.75 (d, J ) 5.0 Hz, 1H), 8.58 (d, J ) 5.9 Hz, 2H),
13
NMR spectra is given for the ring tautomer 17, mainly present
under the trans configuration (4RS,7SR). The assignment of the
structure 17 is strongly supported by the shielded H4 resonance
7.51 (s, 1H), 7.48-7.43 (m, 3H); C NMR (63 MHz, DMSO-d )
6
δ 167.0 (Cq), 157.3 (Cq), 153.1 (CH), 149.9 (2 × CH), 149.2 (Cq),
144.7 (CH), 126.1 (Cq), 120.5 (2 × CH), 117.8 (CH), 86.3 (Cq);
+
+
MS (ESI, positive mode) m/z 477 (2M + Na ), 250 (M + Na ),
(3.52 ppm) with respect to the one in the minor chain tautomer
+
2
28 (M + H ); HRMS (ESI) calcd for C12
10 3 2
H N O , 228.0773;
1
8 (4.96 ppm), by the characteristic chemical shift of the
3
found, 228.0771.
tetrahedral C7 (88.5 ppm), by the strong J correlation between
H8 and C4 observed in the H- C HMQC-LR spectrum, and
by data previously published for the INH-NAD(P) adducts.
1
13
1-Hydroxy-1-(pyridin-4-yl)-1,2-dihydro-3H-pyrrolo[3,4-c]py-
ridin-3-one (5), Prepared from 14. A solution of 14 (200 mg,
9
0.64 mmol) in formic acid (24 mL) was refluxed for 24 h, and the
In UV spectra, these compounds showed one maximum of
absorption at 330 nm, characteristic of the presence of the
dihydropyridine moiety.
solvent was evaporated. Water (10 mL) was added to the residue,
and it was extracted with dichloromethane, and the organic phase
was washed with saturated NaHCO
3
solution. Combined organic
In summary, we have developed two routes for accessing the
unprecedented azaindolinone 5 (stable form of the 4-isonico-
extracts were dried over Na SO , filtered, and concentrated in
vacuum. The crude, without further purification, was stirred at room
2
4
J. Org. Chem, Vol. 72, No. 2, 2007 677

temperature with a NH
evaporation of the solvent, the residue was dissolved in SOCl
8 mL) and refluxed for 2 h. The reaction mixture was concentrated,
3
/MeOH solution (24 mL) for 2 days; after
atmosphere for 1.5 h, and then acetone (2.0 mL) and water (15
mL) were added. The reaction mixture was extracted with dichlo-
romethane, and the organic phase was dried over Na SO , filtered,
2 4
2
(
dissolved in dichloromethane, and the solvent was removed in
vacuum. The last operation was done twice. The paste obtained
was dissolved in acetone (8 mL), and then aqueous ammonia
solution (6 mL) was added dropwise. The mixture was stirred at
room temperature for 2 h, diluted with water (10 mL), and extracted
and concentrated in a vacuum to give the alcohol-amide 14 as a
mixture of two diastereoisomers (rotamers) (154 mg, 90%): IR
-1
(KBr, νmax/cm ) 3057, 2982, 2967, 2359, 2341, 1622, 1604, 1582,
1
1558; H NMR (250 MHz, CDCl ) δ 8.63 (d, J ) 4.9 Hz, 1H),
3
8.54-8.47 (m, 5H), 8.42 (s, 1H), 8.38 (s, J ) 5.9 Hz, 1H), 7.40
(d, J ) 4.9 Hz, 1H), 7.30-7.20 (m, 5H), 5.94 (s, 1H), 5.64 (s,
1H), 3.64 (m, 1H), 3.46 (m, 2H), 3.31 (m, 1H), 1.50 (d, J ) 6.6
Hz, 6H), 1.40 (d, J ) 6.8 Hz, 3H), 1.25 (d, J ) 6.8 Hz, 3H), 1.17
(d, J ) 6.4 Hz, 3H), 1.12 (d, J ) 6.6 Hz, 3H), 0.78 (d, J ) 6.6 Hz,
with ethyl acetate. The organic phase was dried over Na
filtered, and concentrated in vacuum. The residue was purified by
column chromatography on silica gel (CH Cl /MeOH 100:0 to 95:
) to give the hemiamidal 5 (145 mg, 77%). The analytical data
obtained were identical to those described for 5 prepared from 9.
-(3-Bromopyridin-4-yl)-1-hydroxy-1,2-dihydro-3H-pyrrolo-
3,4-c]pyridin-3-one (9). To a solution of 3,4-pyridinedicarbox-
2 4
SO ,
2
2
5
3 H), 0.51 (d, J ) 6.6 Hz, 3H); 13C NMR (63 MHz, CDCl
3
) δ
1
168.8 (Cq), 168.2 (Cq), 151.7 (Cq), 151.0 (CH), 150.5 (Cq), 149.9
(CH), 149.6 (4 × CH), 147.6 (CH), 145.9 (CH), 132.2 (Cq), 131.8
(Cq), 125.1 (CH), 122.4 (CH + Cq), 122.1 (Cq), 121.2 (4 × CH),
74.6 (CH), 70.5 (CH), 51.6 (2 × CH), 46.6 (2 × CH), 20.6, 20.3,
[
imide 8 (1.0 g, 6,8 mmol) and 3-bromopyridine (1.4 mL, 14.9
mmol) in dry THF (60 mL), under argon at -95 °C, was added
lithium diisopropylamide (8.1 mL, 2.0 M in THF/n-heptane, 16.2
mmol) dropwise. The mixture was stirred at -80 °C for 1 h and
then allowed to warm to room temperature over 4 h. Water was
added, and the solvent was evaporated under vacuum. The brown
+
+
20.0 (8 × CH
3
3 2
); MS (EI) m/z 313 (M ), 270 (M - CH(CH ) ),
+
252 (M - CH(CH
3
)
2
2
- H O).
Preparation of the Mixture of Ethyl[1-hydroxy-3-oxo-1-
(
pyridin-4-yl)-1,2,5,7a-tetrahydro-3H-pyrrolo[3,4-c]pyridin-5-
2 2
paste was purified by silica gel column chromatography (CH Cl /
MeOH 100:0 to 80:20). The yellow solid was recrystallized in
yl]acetate 17 and Ethyl(3-aminocarbonyl-4-isonicotinoyl-1,4-
dihydropyridin-1-yl)acetate 18. The reaction medium (100 mM
phosphate buffer, pH 7.5, 15 mL final volume) containing INH (2
acetone to give the hemiamidal 9 as a white solid (100 mg, 5%):
-1
mp 229-239 °C (decomposition); IR (KBr, νmax/cm ) 3178, 3075,
III
mM), 16 (2 mM), and Mn pyrophosphate (4 mM) was stirred at
1
2
6
801, 1959, 1708, 1612; H NMR (250 MHz, DMSO-d ) δ 9.43 (s
room temperature for 20 min. The reaction mixture was chromato-
graphed through a Sep Pak Vac20 cc (5 g) C18 cartridge with a 4
mM NH OAc aqueous solution. Then, careful washing with water,
4
br, 1H), 8.92 (d, J ) 1.0 Hz, 1H), 8.75 (d, J ) 5.0 Hz, 1H), 8.69
(
(
d, J ) 5.1 Hz, 1H), 8.64 (s, 1H), 8.17 (d, J ) 5.0 Hz, 1H), 7.57
s br, 1H), 7.28 (dd, J ) 1.0 and 5.0 Hz, 1H); 13C NMR (63 MHz,
followed by elution with acetonitrile, and concentration to dryness
under vacuum afforded the desired compound as an unstable
mixture of ring (17) and chain (18) structures in 57% yield (65-
DMSO-d
(
6
) δ 168.0 (Cq), 155.7 (Cq), 153.2 (CH), 153.1 (CH), 148.9
CH), 146.3 (Cq), 144.3 (CH), 128.4 (Cq), 124.6 (CH), 118.6 (Cq),
1
17.5 (CH), 85.4 (Cq); MS (ESI, positive mode) m/z 329 (M +
1
8
(
5% of the ring tautomer): H NMR (250 MHz, DMSO-d
6
) δ 8.77
+
+
+
Na ), 307 (M + H ), 288 (M + H - H
for C12 BrN , 305.9878; found, 305.9872.
-Isonicotinoyl-N,N-diisopropylnicotinamide (13). To a solu-
tion of N,N-diisopropylnicotinamide (10) (1.0 g, 4.85 mmol) in ether
2
O); HRMS (ESI) calcd
s br, 2H, chain form), 8.54 (s br, 2H, ring form), 8.09 (s, 1H, NH,
H
8
3 2
O
ring form), 7.86 (d, J ) 5.9 Hz, 2H, chain form), 7.50 (d, J ) 4.1
Hz, 2H, ring form), 7.21 (d, J ) 1.1 Hz, 1H, chain form), 6.83 (s,
4
1
1
H, ring form), 6.33 (s, 1H, OH, ring form), 6.11 (d, J ) 7.8 Hz,
H, chain form), 6.03 (d, J ) 7.8 Hz, 1H, ring form), 4.96, (dd,
(
125 mL) at -78 °C was added lithium diisopropylamide (3.64
mL, 2.0 M in THF/n-heptane, 7.28 mmol) dropwise. After 15 min
stirring, a solution of N-methyl-N-methoxy isonicotinamide (12)
J ) 4.5 and 1.0 Hz, 1H, chain form), 4.64 (dd, J ) 7.8 and 4.5 Hz,
1
4
H, chain form), 4.52 (dd, J ) 7.6 and 1.4 Hz, 1H, ring form),
.22-4.03 (m, 2 × 2H + 2 × 2H, chain + ring form), 3.52 (d,
(
°
886 mg, 5.34 mmol) in ether (10 mL) was added dropwise at -78
C, and the mixture was allowed to warm to room temperature
J ) 1.7 Hz, 1H, ring form), 1.19 (m, 2 × 3H, chain + ring form);
over 3 h. Water was added to quench the reaction, and the mixture
was concentrated in vacuum. The residue was purified by silica
13
6
C NMR (125 MHz, DMSO-d ; the pics assignment could be done
only for the ring tautomer 17) δ 171.3 (Cq), 170.3 (Cq), 153.8
Cq), 149.9 (2 × CH), 133.7 (CH), 133.0 (CH), 121.2 (2 × CH),
01.7 (Cq), 96.9 (CH), 88.5 (Cq), 61.1 (CH ), 53.7 (CH ), 46.5
CH), 14.3 (CH ); MS (FAB, MMBA) m/z 316 (M + H ); UV
CH CN) λmax 330 nm.
gel column chromatography (CH
2
Cl
2
/MeOH 100:0 to 95:5) to afford
(
-
1
1
3 (590 mg, 39%): IR (KBr, νmax/cm ) 3418, 3012, 2967, 2931,
1
(
(
2
2
+
1
1688, 1629, 1582, 1556; H NMR (250 MHz, CDCl
3
) δ 8.74 (dd,
3
J ) 4.3 and 1.7 Hz, 2H), 8.68 (d, J ) 5.0 Hz, 1H), 8.60 (s, 1H),
.53 (dd, J ) 4.5 and 1.5 Hz, 2H), 7.26 (d, J ) 4.9 Hz, 1H), 3.79
m, 1H), 3.42 (m, 1H), 1.32 (d, J ) 6.7 Hz, 6H), 1.18 (d, J ) 6.5
3
7
(
Supporting Information Available: The general experimental
methods are provided, and preparation of compounds 12 and 16 is
13
Hz, 6H); C NMR (63 MHz, CDCl
3
) δ 194.3 (Cq), 167.0 (Cq),
1
1
2
50.8 (2 × CH), 149.7 (CH), 147.1 (CH), 143.0 (Cq), 141.9 (Cq),
described. A compound characterization checklist and copies of a
33.8 (Cq), 122.7 (2 × CH), 122.3 (CH), 51.9 (CH), 46.3 (CH),
1
13
H NMR spectrum and/or a proton-decoupled C NMR spectrum
0.6 (2 × CH
3
), 20.1 (2 × CH
3 3
); MS (DCI, NH ) m/z 329 (M +
1
13
for each new compound, along with two-dimensional H- C
+
+
NH
4
), 312 (M + H ).
1
1
13
3
HSQC J and H- C HMBC J correlations for the mixture of
compounds 17/18, are included. This material is available free of
charge via the Internet at http://pubs.acs.org.
4
-[Hydroxy(pyridin-4-yl)methyl]-N,N-diisopropylnicotin-
mide (14). To a solution of the ketoamide 13 (170 mg, 0.55 mmol)
in ethanol (27 mL) was added NaBH (131 mg, 2.7 mmol). The
reaction mixture was stirred at room temperature under an argon
4
JO062100E
6
78 J. Org. Chem., Vol. 72, No. 2, 2007