Reaction SMILES: [CH3:1][O:2][C:3]([C:5]1[C:9]2[C:10](SC)=[N:11][CH2:12][CH2:13][C:8]=2[N:7]([CH2:16][CH2:17][C:18]2[CH:23]=[CH:22][C:21]([N+:24]([O-:26])=[O:25])=[CH:20][CH:19]=2)[CH:6]=1)=[O:4].[CH3:27][O:28][CH:29]([O:32][CH3:33])[CH2:30][NH2:31]>CO>[CH3:1][O:2][C:3]([C:5]1[C:9]2[C:10]([NH:31][CH2:30][CH:29]([O:32][CH3:33])[O:28][CH3:27])=[N:11][CH2:12][CH2:13][C:8]=2[N:7]([CH2:16][CH2:17][C:18]2[CH:23]=[CH:22][C:21]([N+:24]([O-:26])=[O:25])=[CH:20][CH:19]=2)[CH:6]=1)=[O:4]
Reactant: COC(=O)c1cn(CCc2ccc([N+](=O)[O-])cc2)c2c1C(SC)=NCC2
Reactant: COC(CN)OC
Solvent: CO
Product: COC(=O)c1cn(CCc2ccc([N+](=O)[O-])cc2)c2c1C(NCC(OC)OC)=NCC2
Temperature: 25 °C
Reaction time: 20 h

Procedure:
To a mixture of 2-(4-Nitro-phenyl)-ethylamino-acetic acid tert-butyl ester in 1 mL pyridine is added N-BOC β-alanine (0.178 mmol), and EDCI (0.214 mmol). After stirring at room temperature for 3½ hours, the pyridine is evaporated at reduced pressure. The remaining oil is taken up in ethyl acetate and washed with dilute hydrochloric acid. The organic layers are combined, dried over Na2SO4, and evaporated in vacuo yielding (3-tert-Butoxycarbonylamino-propionyl)-[2-(4-nitro-phenyl)-ethyl]-α-amino-acetic acid tert-butyl ester, 78 mg yellow oil: 1H NMR (CD3OD) 1.45 (d, 9H), 1.50 (d, 9 h), 2.46-2.48 (m, 2H), 2.98-3.08 (m, 2H), 3.27-3.35 (m, 2H), 3.62-3.75 (m, 2H), [4.03, 4.11] (s, 2H), 7.56-7.59 (m, 2H), 8.20-8.23 (m, 2H); LRMS calcd 451.52, found [M] 451.2. Step 3: To a mixture of {(3-tert-Butoxycarbonylamino-propionyl)-[2-(4-nitro-phenyl)-ethyl]-amino}-acetic acid tert-butyl ester (2.5 mmol) in 11 mL THF is 22 mL water added, followed by NaOH (17.5 mmol). After heating at 60° C. for 5½ hours it is quenched with acetic acid (20 mmol). It is placed in the refrigerator for 2½ days. The THF is evaporated off, and the remaining water is extracted several times with EtOAc. The organic layers are combined, dried over Na2SO4 and evaporated in vacuo yielding {(3-tert-Butoxycarbonylamino-propionyl)-[2-(4-nitro-phenyl)-ethyl]-amino}-acetic acid, 983 mg, as a dark yellow/brown oil/foam (99%): 1H NMR (CD3OD) 1.40 (d, 9H), 2.44-2.45 (m, 2H), [2.98, 3.03] (t, 2H), 3.22-3.30 (m, 2H), [3.60, 3.65] (t, 2H), 4.06 (s, 2H), [7.52, 7.54] (d, 2 h), 8.16 (t, 2H); LRMS calcd 395.42, found [M−H] 394.0. Step 4: To a mixture of {(3-tert-Butoxycarbonylamino-propionyl)-[2-(4-nitro-phenyl)-ethyl]-amino}-acetic acid (0.253 mmol) in 1 ml acetic anhydride is dimethyl acetylene dicarboxylate (0.278 mmol) added. After stirring at 85° C. for 4½ hours the solvent is evaporated in vacuo. The dark brown oil is chromatographed using ethyl acetate 2: Hexane 3 as a mobile phase to yield 2-(2-tert-Butoxycarbonylamino-ethyl)-1-[2-(4-nitro-phenyl)-ethyl]-1H-pyrrole-3,4-dicarboxylic acid dimethyl ester, 79 mg, as a yellow oil (66%): 1H NMR (CD3OD) 1.50 (s, 9H), 2.84 (t, 2H), 3.14-3.34 (m, 4H), 3.77 (s, 3H), 3.82 (s, 3H), 4.33 (t, 2H), 6.74 (t, 1H), 7.29 (s, 1H), 7.44 (d, 2H), 8.16 (d, 2H); LRMS calcd 475.50, found [M] 475.1. Step 5: A solution of 2-(2-tert-Butoxycarbonylamino-ethyl)-1-[2-(4-nitro-phenyl)-ethyl]-1H-pyrrole-3,4-dicarboxylic acid dimethyl ester (0.292 mmol) in 10 HCl/ethyl acetate is stirred at RT for ½ hour. The solvent is evaporated in vacuo and placed on the high vacuum pump for several hours yielding 139 mg white solid 1H NMR (CD3OD) 2.92-2.94 (m, 2H), 2.97-2.99 (m, 2H), 3.20 (t, 3H), 3.75 (s, 3H), 3.79 (s, 3H), 4.26 (t, 2H), 7.33 (d, 3H), 8.15 (d, 2H). LRMS calcd 375.38, found [M+H] 376.2) which is stirred in 7 mL THF with triethylamine (1.168 mmol) at 60° C. for 16 hours. The solvent is evaporated in vacuo and chromatographed using ethyl acetate 9: MeOH 1 as mobile phase to yield 1-[2-(4-Nitro-phenyl)-ethyl]-4-oxo-4,5,6,7-tetrahydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester, 73 mg, as a white solid (73%): 1H NMR (CD3OD) 2.47 (t, 2H), 3.16 (t, 2H), 3.23-3.33 (m, 2H), 3.74 (s, 3H), 4.23 (t, 2H), 7.30 (t, 3H), 8.11 (d, 2H); LRMS calcd 343.33, found [M+H] 344.2. Step 6: In a round bottom flask under N2 atm. are the 1-[2-(4-Nitro-phenyl)-ethyl]-4-oxo-4,5,6,7-tetrahydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester (48.64 mmol), P4S10 (24.32 mmol) and 240 mL pyridine combined and heated at 65° C. for 8 hours. After cooling to RT it is poured over ˜600 mL ice and stirred for 2 hours. The yellow solid is filtered off, washed (2×) with water and dried on the high vacuum for 18 h to yield 1-[2-(4-Nitro-phenyl)-ethyl]-4-thioxo-4,5,6,7-tetrahydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester, 10.24 g, as a yellow solid (65%): 1H NMR (CD3OD) 2.43 (t, 2H), 3.16 (t, 2H), 3.28-3.33 (m, 2H), 3.75 (s, 3H), 4.21 (t, 2H), 7.16 (s, 1H), 7.30 (d, 2H), 8.13 (d, 2H); LRMS calcd 359.41, found [M+H] 360.2. Step 7: To a solution of 1-[2-(4-Nitro-phenyl)-ethyl]-4-thioxo-4,5,6,7-tetrahydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester (28.16 mmol) in 130 mL acetone is MeI (56.32 mmol) and K2CO3 (84.48 mmol) added. The reaction mixture is stirred at RT for 2½ hours whereby the acetone is evaporated in vacuo. The remaining oil is taken up in Dichloromethane and washed two times with water. The organic solvents are collected, dried over Na2SO4 and evaporated in vacuo to yield 4-Methylsulfanyl-1-[2-(4-nitro-phenyl)-ethyl]-6,7-dihydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester, 9.46 g, as a yellow foam (90%); 1H NMR (CD3OD) 2.34-2.39 (m, 5H), 3.21 (t, 2H), 3.56 (t, 2H), 3.80 (s, 3H), 4.29 (t, 2H), 7.32-7.38 (m, 3H), 8.17 (d, 2H); LRMS calcd 373.43, found [M+H] 374.2. Step 8: In a round bottom flask are 4-Methylsulfanyl-1-[2-(4-nitro-phenyl)-ethyl]-6,7-dihydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester (25.33 mmol), amino acetaldhyde dimethyl acetal (63.32 mmol) and 125 mL MeOH combined (a part “oiled-out” that later went into solution) and stirred at RT for 20 hours. The solvent is evaporated in vacuo yielding 4-(2,2-Dimethoxy-ethylamino)-1-[2-(4-nitro-phenyl)-ethyl]-6,7-dihydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester, 11.56 g, as a yellow oil/solid that is used without purification. Step 9: To a solution of 4-(2,2-Dimethoxy-ethylamino)-1-[2-(4-nitro-phenyl)-ethyl]-6,7-dihydro-1H-pyrrolo[3,2-c]pyridine-3-carboxylic acid methyl ester (25.33 mmol) in 125 mL MeOH is 10 mL HCl conc. added. It is heated at 63° C. for 15 hours. Since the reaction is not complete another 5 mL HCl conc. is added, and it is heated again at 63° C. for 10 hours. The solvent is evaporated in vacuo, and the remaining oil is dissolved in MeOH whereby K2CO3 (1.2 eq.) is added. After stirred at RT for 1 h the solid is filtered off, washed with MeOH and the filtrate is evaporated in vacuo yielding a yellow solid that is protonated. The protonated product is stirred in Dichloromethane and saturated NaCO3 sol. until everything dissolved. The two layers are separated and the water layer is extracted two times with dichloromethane. The organic layers are collected, dried and evaporated in vacuo yielding a free base which is triturated in ethyl acetate yielding 6-[2-(4-Nitro-phenyl)-ethyl]-5,6-dihydro-4H-1,3a,6-triaza-as-indacene-8-carboxylic acid methyl ester, 9.11 g, as a yellow solid (77%): 1H NMR (CD3OD) 2.76 (t, 2H), 3.18 (t, 2H), 3.78 (s, 3H), 4.07 (t, 2H), 4.28 (t, 2H), 6.94 (s, 1H), 7.01 (s, 1H), 7.31 (d, 3H), 8.10 (d, 2H); LRMS calcd 366.38, found [M+H] 367.2. Step 10: To a solution of 6-[2-(4-Nitro-phenyl)-ethyl]-5,6-dihydro-4H-1,3a,6-triaza-as-indacene-8-carboxylic acid methyl ester (19.67 mmol) in 100 mL DMF is treated with sodium hydride (60%, 1.97 g, 49.18 mmol) portion wise. The reaction is complete in about 2 h at 20° C. Chloroform is added and the reaction mixture is cooled to 5° C. before the dropwise addition of acetic acid (3.15 mL, 55.08 mmol) until pH of 1-3. A saturated solution of aqueous KHCO3 (150 mL) is added, stirred and separated. The separated organic phase is washed with water twice. The filtrate is concentrated directly. Most of the DMF is removed by high vacuum to give a brown wet solid. The wet solid is cooled to room temp. Ether is added, stirred, and filtered to give a brown solid which is dried in air overnight to give 5,6-dihydro-4H-1,3a,6-triaza-as-indacene-8-carboxylic acid methyl ester, 9.11 g, (77%): 1H NMR (CD3OD) 3.05 (t, 2H), 3.86 (s, 3H), 4.25 (t, 2H), 6.97 (s, 1H), 7.05 (s, 1H), 7.40 (s, 1H); LRMS calcd 217.23, found [M−H] 216.1.