Descladinosyl erythromycin in phosgene-assisted cyclic 3,6-ether formation

Erythromycin A has been converted into a 3,6-bridged ether via a C-3 chloroformate by nucleophilic addition of the hydroxyl function at C-6. Further transformations afforded N-demethyl-3-O-descladinosylerythromycin A 2′,3′-carbamate-11,12-carbonate-3,6-ether in 59% overall yield over four reaction steps from (9E)-erythromycin A 9-(O-allyloxime).