Luciferin Analogues Bearing an Amino Group
2-Cyano-6-dimethylaminoquinoline (6): Formaldehyde (90 mg, 3.1 mmol)
was dissolved in THF (30 mL) before H2SO4 (180 mm, 2 mL, 360 mmol)
was added, and the solution was stirred at room temperature for a few
minutes. A solution of 4 (55 mg, 320 mmol) and sodium borohydride
(17 mg, 450 mmol) in THF (30 mL) was added and the reaction mixture
was stirred at room temperature. After 30 min, water and brine were
added to the reaction mixture, and the aqueous layer was removed and
extracted with ethyl acetate. The combined organic extract was dried
over Na2SO4, filtered, and the solvent evaporated. The product was puri-
fied by silica gel column chromatography (ethyl acetate/n-hexane=1:3)
to give a solid (19 mg, 30%). 1H NMR (300 MHz, CD3OD): d=8.16 (d,
J=8.1 Hz, 1H), 7.87 (d, J=9.6 Hz, 1H), 7.61 (d, J=8.1 Hz, 1H), 7.57
(dd, J=2.9, 9.6 Hz, 1H), 6.91 (d, J=2.9 Hz, 1H), 3.14 ppm (s, 6H);
13C NMR (75 MHz, CD3OD): d=151.8, 143.2, 136.1, 132.6, 130.7, 128.3,
124.8, 122.2, 119.3, 104.5, 40.4 ppm; HRMS (EI+): m/z calcd for
C12H11N3: 197.0953 [M+]; found: 197.0965.
2-Cyano-6-methylaminonaphthalene (10): The preparation of 10 from 9
was carried out by the same method as that used to obtain 5. 1H NMR
(300 MHz, CDCl3): d=8.01 (s, 1H), 7.60–7.66 (m, 2H), 7.46 (d, J=
8.8 Hz, 1H), 6.93 (dd, J=2.9, 8.8 Hz, 1H), 6.73 (d, J=2.9 Hz, 1H), 4.23
(br, 1H), 2.96 ppm (s, 3H); 13C NMR (75 MHz, CD3OD): d=149.3,
137.1, 133.7, 129.4, 127.0, 126.6, 125.8, 120.2, 119.2, 103.9, 102.8,
30.2 ppm; HRMS (EI+): m/z calcd for C12H10N2: 182.0844 [M+]; found:
182.0839.
d-(À)-2-(6’-Methylamino-2’-naphthyl)-D2-thiazoline-4-carboxylic
acid
(NMAL): NMAL was prepared from 10 by the same method as that
used to obtain NAL. 1H NMR (300 MHz, [D6]DMSO): d=8.04 (s, 1H),
7.73–7.78 (m, 2H), 7.62 (d, J=8.8 Hz, 1H), 7.00 (dd, J=2.2, 8.8 Hz, 1H),
6.70 (d, J=2.2 Hz, 1H), 5.28 (t, J=8.8 Hz, 1H), 3.71 (dd, J=8.8, 11.3 Hz,
1H), 3.60 (dd, J=8.8, 11.3 Hz, 1H), 2.79 ppm (s, 3H); 13C NMR
(75 MHz, [D6]DMSO): d=172.0, 168.7, 149.5, 137.1, 129.6, 129.3, 125.6,
125.2, 124.7, 124.6, 118.9, 101.4, 78.0, 34.7, 29.5 ppm; HRMS (ESI+): m/z
calcd for C15H14N2O2S: 287.0854 [M+H]+; found: 287.0811.
d-(À)-2-(6’-Dimethylamino-2’-quinolyl)-D2-thiazoline-4-carboxylic acid
(QDMAL): QDMAL was prepared from 6 by the same method as that
used to obtain QAL. 1H NMR (300 MHz, CD3OD): d=8.02–8.11 (m,
2H), 7.91 (d, J=9.5 Hz, 1H), 7.45 (dd, J=2.7, 9.2 Hz, 1H), 6.91 (d, J=
2.7 Hz, 1H), 5.23 (t, J=9.5 Hz, 1H), 3.50–3.65 (m, 2H), 3.10 ppm (s,
6H); 13C NMR (75 MHz, [D6]DMSO): d=171.9, 171.8, 149.3, 145.6,
140.4, 134.2, 130.5, 129.9, 119.9, 118.8, 104.2, 78.9, 33.5 ppm; HRMS
(ESI+): m/z calcd for C15H15N3O2S: 302.0963 [M+H]+; found: 302.0930.
2-Cyano-6-dimethylaminonaphthalene (11): The preparation of 11 from 9
was carried out by the same method as that used to obtain 6. 1H NMR
(300 MHz, CDCl3): d=8.03 (s, 1H), 7.72 (d, J=9.3 Hz, 1H), 7.64 (d, J=
8.8 Hz, 1H), 7.45 (d, J=8.8 Hz, 1H), 7.20 (dd, J=2.5, 9.3 Hz, 1H), 6.86
(d, J=2.5 Hz, 1H), 3.12 ppm (s, 6H); 13C NMR (100 MHz, CDCl3): d=
150.3, 136.7, 133.8, 129.5, 126.9, 126.8, 125.0, 120.3, 116.9, 105.2, 104.0,
40.4 ppm; HRMS (EI+): m/z calcd for C13H12N2: 196.1000 [M+]; found:
196.0987.
2-Amino-6-bromonaphthalene (8):
naphthalene (7) (0.99 g, 4.4 mmol), dioxane (25 mL),
A
mixture of 2-hydroxy-6-bromo-
solution of
a
d-(À)-2-(6’-Dimethylamino-2’-naphthyl)-D2-thiazoline-4-carboxylic acid
(NDMAL): NDMAL was prepared from 11 by the same method as that
used to obtain NAL. 1H NMR (300 MHz, CD3OD): d=8.33 (d, J=
1.5 Hz, 1H), 7.88 (d, J=9.5 Hz, 1H), 7.81 (dd, J=1.5, 8.9 Hz, 1H), 7.73
(d, J=8.9 Hz, 1H), 7.33 (dd, J=2.2, 9.5 Hz, 1H), 7.04 (d, J=2.2 Hz, 1H),
5.43–5.50 (m, 1H), 3.94–4.00 (m, 2H), 3.14 ppm (s, 6H); 13C NMR
(75 MHz, [D6]DMSO): d=172.0, 168.3, 149.7, 136.4, 129.8, 129.1, 126.1,
125.4, 124.9, 124.7, 116.6, 105.0, 78.3, 40.0, 34.8 ppm; HRMS (ESI+): m/z
calcd for C16H16N2O2S: 301.1011 [M+H]+; found: 301.1055.
NaHSO3 (10 g) in water (15 mL) and NH4OH (25 mL) was heated in a
pressure vessel at 2008C for 27 h. After cooling, the vessel was opened
and the dioxane was evaporated. The residue was extracted with ethyl
acetate, and the organic layer was washed with brine, dried over Na2SO4,
filtered, and the solvent evaporated. The product was purified by silica
gel column chromatography (ethyl acetate/n-hexane=1:3) to give a solid
(0.76 g, 77%). 1H NMR (300 MHz, CDCl3): d=7.84 (s, 1H), 7.57 (d, J=
9.5 Hz, 1H), 7.39–7.49 (m, 2H), 6.93–6.99 (m, 2H), 3.88 ppm (br, 2H);
13C NMR (75 MHz, CDCl3): d=144.5, 133.3, 129.6, 129.5, 128.9, 128.3,
127.4, 119.0, 115.6, 108.3 ppm; HRMS (EI+): m/z calcd for C10H8BrN:
223.9898 [M+]; found: 223.9870.
2-Hydroxy-4-nitrobenzaldehyde (13): 2-Methoxy-4-nitrobenzaldehyde 12
(0.40 g, 2.2 mmol) was dissolved in CH2Cl2 (50 mL), to which a solution
of BBr3 in CH2Cl2 (1m, 8 mL) was added at À788C. The solution was
stirred under an Ar atmosphere at room temperature for 19 h. When
TLC monitoring showed the complete consumption of 12, the reaction
mixture was poured into an ice bath. The aqueous layer was separated
and extracted with ethyl acetate. The combined organic layers were
washed with brine, dried over Na2SO4, filtered, and the solvent evaporat-
ed. The product was purified by silica gel column chromatography
6-Amino-2-cyanonaphthalene (9): A solution of 8 in DMF (2 mL) was
prepared, and CuCN (0.81 g, 9.0 mmol) was added. The reaction mixture
was heated at reflux under an Ar atmosphere for 2 h. When TLC moni-
toring showed the complete consumption of 8, the mixture was poured
into NaH2PO4 buffer and extracted with ethyl acetate. The organic layer
was washed with brine, dried over Na2SO4, filtered, and the solvent
evaporated. The product was purified by silica gel column chromatogra-
phy (ethyl acetate/n-hexane=1:3) to give a solid (0.15 g, 27%). 1H NMR
(300 MHz, CDCl3): d=8.05 (s, 1H), 7.69 (d, J=8.8 Hz, 1H), 7.61 (d, J=
8.8 Hz, 1H), 7.47 (d, J=8.8 Hz, 1H), 7.02 (dd, J=2.2, 8.8 Hz, 1H), 6.96
(d, J=2.2 Hz, 1H), 4.12 ppm (br, 2H); 13C NMR (75 MHz, CDCl3): d=
147.1, 136.7, 134.0, 130.0, 127.0, 126.6, 126.4, 120.0, 119.4, 107.8,
105.0 ppm; HRMS (EI+): m/z calcd for C11H8N2: 168.0687 [M+]; found:
168.0666.
(CH2Cl2/n-hexane=2:1) to give
a
solid (0.34 g, 91%). 1H NMR
(300 MHz, CDCl3): d=11.16 (s, 1H), 10.06 (s, 1H), 7.77–7.87 ppm (m,
3H); 13C NMR (75 MHz, CDCl3): d=195.9, 161.9, 152.5, 134.7, 123.7,
114.3, 113.4 ppm; MS (EI+): m/z: 167 [M+].
3-Cyano-7-nitrocoumarin (14): Malonitrile (0.13 g, 2.0 mmol) and 13
(0.25 g, 1.5 mmol) were dissolved in NaHCO3 (aqueous, 0.1m, 10 mL)
and the reaction mixture was stirred at room temperature for 2 h. HCl
(conc., 1 mL) was added to the mixture, which was heated at reflux for
1 h. The precipitate was collected by filtration and dried under high
vacuum to afford pure 14 (0.29 g, 89%) 1H NMR (300 MHz,
[D6]DMSO): d=9.05 (s, 1H), 8.34 (d, J=2.2 Hz, 1H), 8.24 (dd, J=2.2,
8.8 Hz, 1H), 8.06 ppm (d, J=8.8 Hz, 1H); 13C NMR (100 MHz,
[D6]DMSO): d=156.1, 153.7, 151.6, 150.4, 131.3, 122.3, 119.8, 114.1,
112.2, 105.7 ppm; HRMS (EI+): m/z calcd for C10H4N2O4: 216.0171
[M+]; found: 216.0356.
d-(À)-2-(6’-Amino-2’-naphthyl)-D2-thiazoline-4-carboxylic acid (NAL):
d-Cysteine hydrochloride monohydrate (98 mg, 560 mmol) was dissolved
in water (5 mL) through which a stream of Ar was bubbled, and the pH
of the solution was adjusted to 9 with potassium carbonate (0.5m). A so-
lution of 9 (33 mg, 200 mmol) in MeOH (10 mL) through which a stream
of Ar was bubbled, was prepared. The d-cysteine solution was added to
the solution of 9, and the mixture was stirred at room temperature under
an Ar atmosphere in the dark. After 12 h, the MeOH was evaporated,
and the residue purified by semipreparative HPLC (eluent A: H2O/0.1%
TFA, eluent B: 80% acetonitrile/20% H2O/0.1% TFA, A/B=80:20 to
20:80 (20 min)) to give a red solid (7 mg, 14%). 1H NMR (300 MHz,
CD3OD): d=8.37 (s, 1H), 7.92 (d, J=8.8 Hz, 1H), 7.87 (d, J=8.8 Hz,
1H), 7.75 (d, J=8.8 Hz, 1H), 7.20–7.26 (m, 2H), 5.47 (t, J=8.1 Hz, 1H),
3.92–4.03 ppm (m, 2H); 13C NMR (75 MHz, [D6]DMSO): d=171.9,
169.5, 169.0, 136.7, 130.2, 129.5, 125.5, 125.4, 124.8, 124.6, 119.3, 106.5,
77.7, 34.7 ppm; HRMS (ESI+): m/z calcd for C14H12N2O2S: 273.0698
[M+H]+; found: 273.0663.
7-Amino-3-cyanocoumarin (15): A solution of 14 (0.29 g, 1.3 mmol) in
MeOH (60 mL) and ethyl acetate (20 mL) was prepared, to which Pd/C
(10%, 0.03 g) was added. The reaction mixture was stirred under a H2 at-
mosphere at room temperature for 20 h. The reaction mixture was fil-
tered, and the filtrate was concentrated and dried under high vacuum to
afford pure 15 (0.23 g, 90%). 1H NMR (300 MHz, [D6]DMSO): d=8.53
(s, 1H), 7.42 (d, J=8.8 Hz, 1H), 7.06 (br, 2H), 6.63 (dd, J=2.2, 8.8 Hz,
1H), 6.43 ppm (d, J=2.2 Hz, 1H); 13C NMR (100 MHz, [D6]DMSO): d=
158.4, 157.5, 156.9, 152.4, 131.7, 116.2, 112.7, 107.4, 97.9, 90.2 ppm;
HRMS (EI+): m/z calcd for C10H6N2O2: 186.0429 [M+]; found: 186.0473.
Chem. Asian J. 2010, 5, 2053 – 2061
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2059