96 3 PROBLEMS Problem 26 An alkaloid of elemental composition C,H, NO, was isolated from the plant Dactylicapros to- rulosa (Fumariaceae). What is the structure of it given its NMR spectra 26? Conditions: CDC13, 25 C, 400 MHz ('H), 100 MHz ("C). (a) 'H NMR spectrum with expanded section; (b,c) C NMR spectra, proton broadband decoupled (bottom) and NOE enhanced coup- led with expanded sections (top), (b) from 8c = 27.6-47.8, (c) from 8c = 101.3-164.2. 26 7 Hz 7.39 6.47 5.36 ppm 3.49 3.00 2.77 60 30 5.0 71 6.3 MM 1620 1644 1741 164.2 150.0 146.5 133.4 123.2 107.7 106.7 101.3 40 3.5 139.1 137.3 129.3 Hz b ppm 17.8 34.8 27.6 6 7 Hz a 7.39 6.47 5.36 ppm 349 3.00 2.77 60 40 3.5 L 139.1 137.3 129.3 Hz b ppm 47.8 34.8 27.6 C T 164.2 150.0 146.5 133.4 123.2 107.7 106.7 101.3 3.5 139.1 137.3 129.3 Hz