A-Nitro ethers

Introduction of the nitro group turned out to be quite a challenge. We learned in early experiments that the a-nitro ether moiety is quite labile hydrolytically. We therefore devised the protecting scheme shown below, to allow us to deblock the bridgehead carboxyl and allylic hydroxyl under mild conditions and unleash the nitronate anion under alkaline conditions as a final step. 

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