Chiral Auxiliaries and Additives

Question 1

chiral auxiliaries

Answer 1

attach to enantiopure molecule and preform enantiopure reaction

Question 2

good auxiliary

Answer 2

readily available in both enantiomers, easy to attach and remove and can induce high diastereoselectivity

Question 3

Schollof bis-lactim amino acid synthesis

Answer 3

condensation to cyclic dipeptide, methylation with Meerwiens salt, deprotonation with strong base, iPr group blocks bottom face of enolate equivalent and new substituent adds trans to valine iPr

Question 4

oxazolidinone chiral auxiliary

Answer 4

enantioselective enolate reactions

Question 5

Evans auxiliary

Answer 5

used for enantioselective enolate reactions

Question 6

cleaving Evans aux

Answer 6

Lithal gives alcohol
NaSEt gives C(O)(SEt)
MeNHOMe.HCl and AlCl3 gives CON(Me)(OMe)
LiOBn gives C(O)(OBn)
LiOOH, water and Na2SO3 gives carboxylic acid

Question 7

Chiral additive

Answer 7

doesn’t form full covalent bond with starting material/transition state, used in stoichiometric amounts