1. Draw compound 13 in your answer book and circle all the protecting groups 
2. What reagent(s) would you choose to selectively remove just the silyl ethers from 13? 
3. Using your answers to parts (v) and (vi) above, explain what is meant by an orthogonal protecting group strategy. 

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TBSO OBn OTPS OBn OTBS TPSO- a. n-BuLi, THE NNHSO2AR H НО 8 10 TBSO TBSO TBSO OTPS ОТPS OTPS c. LIAIH4, Et,0 OBn OBn OBn d. Но Но H. to НО to 11 13 12 TPS = tert-butyldiphenylsilyl (-Si((C6H5)2C(CH3)3)) TBS = tert-butyldimethylsilyl (-Si((CH3)2C(CH3)3)) Bn = benzyl (CH2PH) acac = acetylacetonato (CH3COCH2COCH3) BuLi = butyl lithium (CH3CH2CH2CH2LI) b. II ..... TBSO OBn OTPS OBn OTBS TPSO- a. n-BuLi, THE NNHSO2AR H НО 8 10 TBSO TBSO TBSO OTPS ОТPS OTPS c. LIAIH4, Et,0 OBn OBn OBn d. Но Но H. to НО to 11 13 12 TPS = tert-butyldiphenylsilyl (-Si((C6H5)2C(CH3)3)) TBS = tert-butyldimethylsilyl (-Si((CH3)2C(CH3)3)) Bn = benzyl (CH2PH) acac = acetylacetonato (CH3COCH2COCH3) BuLi = butyl lithium (CH3CH2CH2CH2LI) b. II .....