Explain the mechanism and reactions that occur in the schematic below! Scheme 4. Deprotection and Deoxygenation Steps Leading to 7a OR (i) TFA OR Me NBOC M NH Meo (ii) BzOCOCI Meo NaHCO3, THE NHCbz OME NHBc 5a,b 6a,b 6a 92% yield 6b 95% yield TFA, silane MS 4 M NH Meo NHCbz 7a 74% yield (failed for 6b) 7a