Journal of Medicinal Chemistry
Article
(2R,12aS)-N-(2,4-Difluorobenzyl)-7-hydroxy-2-methyl-6,8-
dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino-
[2,1-b][1,3]oxazine-9-carboxamide (15) and (2S,12aR)-N-(2,4-
Difluorobenzyl)-7-hydroxy-2-methyl-6,8-dioxo-3,4,6,8,12,12a-
hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-
(R)-N-(4-Fluorobenzyl)-7-hydroxy-3,3-dimethyl-6,8-dioxo-
3,4,6,8,12,12a-hexahydro-2H-[1,3]oxazino[3,2-d]pyrido[1,2-a]-
pyrazine-9-carboxamide (31) and (S)-N-(4-Fluorobenzyl)-7-
hydroxy-3,3-dimethyl-6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-
[1,3]oxazino[3,2-d]pyrido[1,2-a]pyrazine-9-carboxamide (32).
Methyl 3-(benzyloxy)-5-((4-fluorobengzyl)carbamoyl)-4-oxo-1-(2-ox-
oethyl)-1,4-dihydropyridine-2-carboxylate (9a) (29 mg, 0.064 mmol),
3-amino-2,2-dimethylpropan-1-ol (17 mg, 2.5 equiv), and 4 drops acetic
acid were mixed in dichloroethane and heated at 80 °C for 1 h. The
reaction was concentrated under reduced pressure, NaHCO3 (aq) was
added, and the mixture was extracted with dichloromethane, dried over
sodium sulfate, and purified using silica-gel chromatography (0−100%
EtOAc/hexanes, gradient elution). This material was separated using
chiral SFC purification (40 mg) (50% methanol/carbon dioxide at 100
bar, 40 °C, 90 mL/min on an AD-H column) to give 12 mg of isomer
1 (first peak to elute) identified to be the S enantiomer and 12 mg peak
2 identified to be the R enantiomer. The peak 2 material, (R)-7-
(benzyloxy)-N-(4-fluorobenzyl)-3,3-dimethyl-6,8-dioxo-3,4,6,8,12,12a-
hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-carbox-
amide (7 mg), and 10 wt % Pd/C (13 mg) were dissolved in MeOH/
THF, and the mixture was stirred at 1 atm H2 for 20 min. The mixture
was filtered through Celite and the pad was rinsed with dichloro-
methane/methanol until no product eluted, and the filtrate was
concentrated under reduced pressure. The sample was suspended in
methanol, and the solid was collected by vacuum filtrated to give desired
product 31 (2 mg, 35%). 1H NMR (400 MHz, CDCl3) δ 12.39 (br s,
1H), 10.39 (m, 1H), 8.33 (s, 1H), 7.32 (m, 2H), 7.00 (t, J = 8.59 Hz,
2H), 4.97 (m, 1H), 4.66−4.55 (m, 2H), 4.44 (m, 1H), 4.34 (m, 1H),
4.18 (m, 1H), 3.71 (m, 1H), 3.57 (m,1H), 2.85 (d, J = 13.28 Hz, 1H),
1.14 − 0.92 (m, 6H). ES+ LC/MS: m/z calcd 415.15; for 31 found
416.15 (M + 1)+, for 32 found 416.14 (M + 1)+.
(4R,12aS)-7-(Benzyloxy)-N-(2,4-difluorobenzyl)-4-methyl-
6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-[1,3]oxazino[3,2-d]-
pyrido[1,2-a]pyrazine-9-carboxamide (27). To the solution of the
compound 9b (705 mg, 1.50 mmol) in dichloromethane (10 mL), (R)-
3-aminobutan-1-ol (200 mg, 2.24 mmol) and acetic acid (10.0 mg, 0.17
mmol) were added. The reaction was performed with a microwave
reaction apparatus at 140 °C for 25 min. After cooling to room tem-
perature, the solvent was evaporated in vacuo and the residue was
subjected to silica gel column chromatography, and fractions eluting
with chloroform−methanol were collected and concentrated to obtain
the product (620 mg, 81% yield) as colorless solid. 1H NMR (CDCl3) δ
8:1.36 (d, J = 7.1 Hz, 4H), 1.50−1.55 (m, 1H), 2.16−2.18 (m, 1H),
3.98−3.99 (m, 2H), 4.11 (dd, J = 13.4, 6.0 Hz, 1H), 4.24 (dd, J = 13.5,
3.9 Hz, 1H), 4.66 (d, J = 5.9 Hz, 2H), 5.01−5.04 (m, 1H), 5.19 (dd, J =
6.0, 3.9 Hz, 1H), 5.29 (d, J = 10.2 Hz, 1H), 5.33(d, J = 9.9 Hz, 1H),
6.79−6.87 (m, 2H), 7.31−7.43 (m, 4H), 7.63−7.65 (m, 2H), 8.36
(s, 1H), 10.42 (s, 1H).
1
carboxamide (16). H NMR (DMSO-d6) δ 12.48 (s, 1H), 10.35 (t,
J = 5.7 Hz, 1H), 8.50 (s, 1H), 7.44−7.35 (m, 1H), 7.29−7.20 (m, 1H),
7.10−7.03 (m, 1H), 5.30 (t, J = 3.9 Hz, 1H), 4.54 (d, J = 5.7 Hz, 2H),
4.58−4.42 (m, 3H), 4.06−3.95 (m, 1H), 3.29−3.18 (m, 1H), 1.75 (d, J =
13.8 Hz, 1H), 1.38 (m, 1H), 1.14 (d, J = 6.0 Hz, 3H). ES+ LC/MS: m/z
calcd 419.13; for 15 found 420.12 (M + 1)+, for 16 found 420.10
(M + 1)+.
(2R,12aS)-N-(2,4-Difluorobenzyl)-2-ethyl-7-hydroxy-6,8-
dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino-
[2,1-b][1,3]oxazine-9-carboxamide (17) and (2S,12aR)-N-(2,4-
Difluorobenzyl)-2-ethyl-7-hydroxy-6,8-dioxo-3,4,6,8,12,12a-
hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-
carboxamide (18). 1H NMR (DMSO-d6) δ 12.48 (s, 1H), 10.34 (br s,
1H), 8.50 (s, 1H), 7.42−7.37 (m, 1H), 7.26−7.21 (m, 1H), 7.07−7.03
(m, 1H), 5.29 (s, 1H), 4.57−4.41 (m, 4H), 3.78−3.73 (m, 1H), 3.22 (t,
J = 10.2 Hz, 1H), 1.75 (d, J = 10.8 Hz, 1H), 1.51−1.40 (m, 3H), 0.87 (d,
J = 5.4 Hz, 3H). ES+ LC/MS: m/z calcd 433.14; for 17 found 434.15
(M + 1)+, for 18 found 434.12 (M + 1)+.
(2S,12aS)-N-(2,4-Difluorobenzyl)-7-hydroxy-2-isopropyl-6,8-
dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino-
[2,1-b][1,3]oxazine-9-carboxamide (19) and (2S,12aR)-N-(2,4-
Difluorobenzyl)-7-hydroxy-2-isopropyl-6,8-dioxo-
3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b]-
[1,3]oxazine-9-carboxamide (20). 1H NMR (DMSO-d6) δ 12.48 (s,
1H), 10.35 (br s, 1H), 8.50 (s, 1H), 7.43−7.37 (m, 1H), 7.26−7.21 (m,
1H), 7.08−7.01 (m, 1H), 5.29 (s, 1H), 4.46−4.41 (m, 5H), 3.59−3.52
(m, 1H), 3.20 (t, J = 8.4 Hz, 1H), 1.78−1.72 (m, 1H), 1.69−1.57 (m,
1H), 1.49−1.41 (m, 1H), 0.86 (dd, J = 13.5, 4.8 Hz, 6H). ES+ LC/MS: m/z
calcd 447.16; for 19 found 448.14 (M + 1)+, for 20 found 448.16 (M + 1)+.
(2S,12aS)-N-(2,4-Difluorobenzyl)-7-hydroxy-2-(methoxy-
methyl)-6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido-
[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-carboxamide (21) and
(2R,12aR)-N-(2,4-Difluorobenzyl)-7-hydroxy-2-(methoxymeth-
yl)-6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]-
pyrazino[2,1-b][1,3]oxazine-9-carboxamide (22). 1H NMR
(CDCl3) δ = 12.33 (br s, 1H), 10.38 (br s, 1H), 8.30 (s, 1H), 7.40−
7.30 (m, 1H), 6.85−6.75 (m, 2H), 5.12 (s, 1H), 4.80−4.70 (m, 1H),
4.64 (d, J = 5.9 Hz, 1H), 4.36 (d, J = 10.1 Hz, 1H), 4.24 (d, J = 13.1 Hz,
1H), 4.11−4.00 (m, 1H), 3.50−3.35 (m, 2H), 3.37 (s, 3H), 3.21−3.09
(m, 1H), 1.80−1.60 (m, 2H). ES+ LC/MS: m/z calcd 449.14; for 21
found 450.12 (M + 1)+, for 22 found 450.14 (M + 1)+.
(2S,12aS)-N-(2,4-Difluorobenzyl)-7-hydroxy-6,8-dioxo-2-
phenyl-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]-
pyrazino[2,1-b][1,3]oxazine-9-carboxamide (23). 1H NMR
(CDCl3) δ 12.45 (s, 1H), 10.38 (s, 1H), 8.50 (s, 1H), 7.42−7.21 (m,
7H), 7.08−7.04 (m, 1H), 5.51 (s, 1H), 4.98 (d, J = 8.7 Hz, 1H), 4.68−
4.54 (m, 5H), 3.49 (t, J = 9.6 Hz, 1H), 1.98 (d, J = 9.6 Hz, 1H), 1.82−
1.70 (m, 1H). ES+ LC/MS: m/z calcd 481.14; found 482.17 (M + 1)+.
(3S,12aS)-N-(4-Fluorobenzyl)-7-hydroxy-3-methyl-6,8-
dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino-
[2,1-b][1,3]oxazine-9-carboxamide (28) and (3R,12aR)-N-(4-
Fluorobenzyl)-7-hydroxy-3-methyl-6,8-dioxo-3,4,6,8,12,12a-
hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-
(4R,12aS)-N-(2,4-Difluorobenzyl)-7-hydroxy-4-methyl-6,8-
dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino-
[2,1-b][1,3]oxazine-9-carboxamide (3). To the solution of com-
pound A (4.3 g, 8.40 mmol) in THF (120 mL), 10% palladium- carbon
powder (400 mg) was added, and the mixture was stirred at room
temperature for 1 h under hydrogen atmosphere. The reaction solution
was filtered with Celite, and the filtrate was evaporated in vacuo. The
residue was dissolved in chloroform, and insoluble residue was filtered
with Celite again, and the filtrate was evaporated in vacuo. The residual
crystals were recrystallized from dichloromethane−methanol to obtain
1
carboxamide (29). H NMR (DMSO-d6) δ 12.45 (s, 1H), 10.36 (t,
J = 5.9 Hz, 1H), 8.52 (s, 1H), 7.38−7.32 (m, 2H), 7.20−7.12 (m, 2H),
5.20 (t, J = 3.8 Hz, 1H), 4.52 (d, J = 5.9 Hz, 2H), 4.60−4.41 (m, 3H),
4.03−3.97 (m, 1H), 3.48 (t, J = 11.1 Hz, 1H), 2.86 (t, J = 12.5 Hz, 1H),
1.93−1.84 (m, 1H), 0.81 (d, J = 6.6 Hz, 3H). ES+ LC/MS: m/z calcd
401.14; for 28 found 402.13 (M + 1)+, for 29 found 402.14 (M + 1)+.
(3R,12aR)-N-(2,4-Difluorobenzyl)-7-hydroxy-3-methyl-6,8-
dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino-
[2,1-b][1,3]oxazine-9-carboxamide (30). 1H NMR (CDCl3) δ
12.37 (s, 1H), 10.38 (br s, 1H), 8.31 (s, 1H), 7.40−7.32 (m, 1H),
6.84−6.80 (m, 2H), 4.98 (t, J = 3.7 Hz, 1H), 4.75−4.65 (m, 1H), 4.63
(d, J = 5.9 Hz, 2H), 4.38−4.30 (dd, J = 14.1, 4.0 Hz, 1H), 4.45−4.05 (m,
2H), 3.41 (dd, J = 12.9, 11.2 Hz, 1H), 2.70 (dd, J = 13.4, 11.6 Hz, 1H),
2.10−2.00 (m, 1H), 0.90 (d, J = 6.9 Hz, 3H). ES+ LC/MS: m/z calcd
419.13; found 420.13 (M + 1)+.
1
the product (2.67 g, 76% yield). H NMR (CDCl3) δ 12.45 (s, 1H),
10.38 (br s, 1H), 8.30 (s, 1H), 7.40−7.30 (m, 1H), 6.85−6.75 (m, 2H),
5.26 (d, J = 5.8, 4.1 Hz, 2H), 5.05−4.95 (m, 1H), 4.64 (d, J = 5.9 Hz,
2H), 4.27 (dd, J = 13.4, 4.2 Hz, 1H), 4.12 (dd, J = 13.6, 6.0 Hz, 1H), 4.05
(t, J = 2.3 Hz, 1H), 4.02 (d, J = 2.2 Hz, 1H), 2.30−2.19 (m, 1H), 1.56
(dd, J = 14.0, 2.0 Hz, 1H), 1.42 (d, J = 7.0 Hz, 3H). ES+ LC/MS: m/z
calcd 419.13; found 420.13 (M + 1)+.
(4R,12aS)-N-(2,4-Difluorobenzyl)-7-hydroxy-4-methyl-6,8-
dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino-
[2,1-b][1,3]oxazine-9-carboxamide (3) sodium salt. After dis-
solution of 18.0 g of compound 12 (1.0 equiv) in 54 mL of EtOH by
heating, followed by filtration, 21.5 mL of 2N NaOHaq (1.0 equiv) was
added to the solution at 80 °C. The solution was gradually cooled to
K
dx.doi.org/10.1021/jm400645w | J. Med. Chem. XXXX, XXX, XXX−XXX