“…The formation of 3a,4-dihydro-3H,7H-and 4H,7H-pyrazolo[4′,3′:5,6]pyrano[4,3c] [1,2]oxazole ring systems was easily deduced after an in-depth analysis of NMR spectral data, which were obtained through a combination of standard and advanced NMR spectroscopy techniques, such as 1 H- 13 C HMBC, 1 H-13 C J-HMBC, 1 H- 15 N HMBC, 1 H- 13 C HSQC, 1 H- 13 C H2BC, 1 H-1 H COSY, 1 H-1 H NOESY and 1,1-ADEQUATE experiments (Figure 1). In the case of compound 5a, the multiplicity-edited 1 H- 13 C HSQC spectrum allowed us to identify the pairs of geminally coupled methylene protons, since both protons displayed cross-peaks with the same carbon. For instance, it showed two pairs of negative signals at δ H 4.66, 3.79 and 4.78, 4.17 ppm, which have one-bond connectivities with the methylene carbons C-3 (δ 69.7 ppm) and C-4 (δ 70.9 ppm), respectively.…”