General procedure for the synthesis of 1-benzyl octahydropyrrolo[3,4-B]pyrrole-5(1H)-carboxylic acid from ethyl 1-benzylhexahydropyrrolo[3,4-B]pyrrole: Ethyl 1-benzyl octahydropyrrolo[2,3-c]pyrrole-5-carboxylate (2.1 g, 7.65 mmol) was dissolved in 37% hydrochloric acid (11 mL), and the reaction was heated and refluxed for 24 hours. Upon completion of the reaction, the pH of the reaction solution was adjusted to 8 with sodium carbonate, followed by multiple extractions of the product with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford 1.4 g of 1-benzyl octahydropyrrolo[3,4-B]pyrrole (90% yield) as a brown oil, which could be used for the next reaction without further purification. Mass spectral analysis (m/z): 203.2 [MH]+.