b) Disaccharide E is a reducing sugar. It is hydrolyzed by an α-glycosidase enzyme, which means it contains an α- glycoside link. Treatment of E with Ag2O and excess MeDgives an octamethyl derivative F. Hydrolysis of F in dilute aqueous acid gives the pair of molecules shown below. Write the structures of E and F. (If the stereochemistry at a particular carbon is not determined by the above data, indicate this with a wavy line as shown below.) HO OMe OMe MeO MeO OH OMe Am OH OMe OMe

Ribose, a carbohydrate with the formula shown, forms a cyclic hemiacetal, which, in principle, could contain either a four-membered, five-membered, or six-membered ring. When D-ribose is treated with methanol in the presence of an acid catalyst, two cyclic acetals, A and B, are formed, both with molecular formula C,H,0, These are separated, and each is treated with sodium periodate (Section 10.8C) followed by dilute aqueous acid. Both A and B yield the same three products in the same ratios. он о CHO СНО H+ CH,OH A +B ÕH 1. NalO, 2. H,0* НО CHO + CHOH + CH,OH ÕH CH,OH Isomeric cyclic acetals with molecular formula CH12O, D-Ribose (C;H1605) From this information, deduce whether the cyclic hemiacetal formed by D-ribose is four- membered, five-membered, or six-membered.

a) For each of the following pairs of compounds, identify them as identical, enantiomers or Note that there are three pairs of compounds. b) Define the stereochemistry (R or S) at all the chiral carbons for only one member of each pair of compounds.

Provide the missing reactants, reagents, or products for the following reaction sequences below. If a sequence leads to a racemic mixture you should indicate "+ enantiomer." [or NH₂ CH,CHÍNH, H* (catalyst) total ele 1. LIAIH4 2. H₂O 0: