benzyl (2S,3R,3aS,3'R,4a'R,6S,6a'R,6b'S,7aR,12a'S,12b'S)-3'-azido-3,6,11',12b'-tetramethyl-2',3,3a,3',4',4a',5,5',6,6',6a',6b',7,7a,7',8',10',12',12a',12b'-icosahydro-1'H,4H-spiro[furo[3,2-b]pyridine-2,9'-naphtho[2,1-a]azulene]-4-carboxylate