Question

Question 5 (21 Marks) So is list Cytovaricin is a macrolide antibiotic that possesses promising antineoplastic activity. In an effort to understand which portion of the molecule is responsible for this biological activity, Prof. David Evans completed a convergent total synthesis. The following question relates to that work. он он Cytovaricin Med OH In Prof. Evan's synthesis, the oxazolinone (A) was deprotonated to generate an enolate (B) with defined stereochemistry, which then participated in an aldol reaction with aldehyde (C) to give the product (D). i. LDA ON enolate (B) e A). O на OPMB iii. H*/H20 recall that LDA = Х OH ЛОРМА PK (D)

Answer 1

(a) ů pa LDA Z-endate) E-endate) Li"- L . - (6) y me @ IMH Н ine L (T.s.] in me & the Favourable ST.3.] nor no favoured ме Н VH ph me me Z-endate Ph me w doesn't E-enolate to Enolate ③ has a (2) stereochemistry. since the steric repulsion in the eyclic Transition stare (T-s) is least, ie, the Is. is favourable for the formation of the are. Therefore, E-enolate doesn't form.