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2-Carboxyphenanthrene (2 g, 0.009 mol) was suspended in dry benzene (50 ml) and heated under reflux in the presence of thionyl chloride (5 ml) for 5 hr. The solvent was removed and the corresponding acid chloride was used without further purification. Piperazine-2,3-dicarboxylic acid (0.508 g, 0.003 mol) was dissolved in a 0.991 M aqueous sodium hydroxide solution (9.4 ml, 0.009 mol), dioxane (10 ml) was added and the solution was cooled to 0° C. A solution of the acid chloride (0.84 g, 0.0035 mol) in dioxane (10 ml) was added to the reaction mixture. The reaction was warmed to room temperature and stirred for 2-3 hr. The reaction mixture was acidified to pH 2-3 with aqueous HCl. The solid was filtered, dissolved in dioxane/ H2O (50:50) and bound to an ion exchange resin (Dowex-AG50 H+ form) chromatography column. It was eluted with dioxane/H2O (50:50) until organic impurities are removed. The column was eluted with 10% aqueous pyridine and the ninhydrin fractions were combined. The solvent was removed and the solid was crystallised from H2O to give a white solid (0.128 g, 12%). m.p.=218.1-221.7 ° C. (dec.); 1H NMR (300 MHz, NaOD/ D2O) 7.7-8.8 (m, 9H, Ar), 5.6 (d, 0.5H, CH—CO2H, JAB=2.6Hz), 4.8 (d, 0.5H, CH—CO2H, JAB=2.6Hz), 4.4 (d, 0.4H, CH—CO2H, JAB=12.0Hz), 3.6 (d, 0.4H, CH—CO2H, JAB=12.0Hz), 2.5-3.8 (m, 4H, N—CH2CH2—NH); Elemental analysis calculated for C21,H18N2O5. 2.3H2O C:60.07, H:5.44, N:6.67. Found C:60.06, H:5.38, N: 6.85. The cis-isomerism was confirmed by COSEY 1H NMR.

1. temperatureheated
2. customThe solvent was removed
3. customthe corresponding acid chloride was used without further purification
4. additionwas added
5. temperatureThe reaction was warmed to room temperature
6. filtrationThe solid was filtered
7. dissolutiondissolved in dioxane/ H2O (50:50)
8. washIt was eluted with dioxane/H2O (50:50) until organic impurities
9. customare removed
10. washThe column was eluted with 10% aqueous pyridine
11. customThe solvent was removed
12. customthe solid was crystallised from H2O