Forming 1,4 Glycosidic Linkages

Question 1

for a mix of alpha/beta

Answer 1

glycosyl donor (all OPg) activate C1 with Lewis acid

glycosyl acceptor Nu has free C4 OH attacks C1

get more alpha b/c anomeric effect

Question 2

exclusively get b-1,4 glycosidic linkage

Answer 2

glucose + excess AcCl, Pyr CH2Cl2

ether lone pair forms db with C1, OAc leaves

HBr, HOAc… Br- attacks C1 top/bottom

Lewis base pulls off Br db reforms with ether

C2 Ac group protects bottom side of C1