Synthesis and Crystal Structure of a Novel Heterocycle, 2-Oxa-4,7-Diazabicyclo[3.3.1]Non-3-Ene

The compound 5 , containing the novel heterocycle 2-oxa-4,7-diazabicyclo[3.3.1]non-3-ene, has been obtained in a synthetic approach toward oxazoles and 1,3-diazepanes of natural product-like complexity from cyclization and rearrangement of δ-lactam cyanamides. When this procedure was applied to a silyl-protected N -(( 3S , 4S , 5S )-4,5-dihydroxy-2-oxopiperidin-3-yl)cyanamide ( 2b ) formation of the novel heterobicyclic scaffold 5 was observed along with the expected oxazole ( 3b ) and diazepane ( 4b ) products. The crystal structures of 5 and diazepane 4b are described. Compound 5 crystallized from methanol in the monoclinic system, P2 1 space group with unit cell parameters a = 15.3402(9), b = 7.2717(4), c = 22.5803(13), β = 106.8620(10) and a cell volume of 2410.5(2) A 3 . Graphical Abstract The synthesis and crystal structure of the title compound is described.