A New Bicyclic Pyrrolidine Block for Nirmatrelvir and Analogues

To study the chemical properties and potential use in the synthesis of Nirmatrelvir and related compounds, a key block, ()-2-ethoxy-6,6-dimethyl-3-azabicyclo[3.1.0]hex-2-ene, which is readily available from (+)-3-carene and obtained by "enol-ethylation" of ()-6,6-dimethyl-3-azabicyclo[3.1.0]hexan-2-one with triethyloxonium tetrafluoroborate ((EtO)BF ), was proposed.