PS Session 7 09.30.10

PS Session 7 09.30.10 - N-Boc valine (below). When H 2 SO 4...

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1 Problem-Solving Session Worksheet Name Chemistry 262, Fall 2010 Session 7: 7 October 2010 1. Provide a mechanism for the DCC coupling reaction illustrated below. 2. The structure of amoxicillin (a common antibiotic) is illustrated below. Construct two distinct retrosynthetic paths by illustrating appropriate precursors for the formation of each of amoxicillin ʼ s two amide bonds by DCC coupling. What groups need to be protected prior to coupling in each case? Ph OH O + NH 2 N C N Cy Cy + Ph NH(CH 2 ) 2 CH 3 O + CyHN NHCy O N S O HN CO 2 H O H 2 N HO
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2 3. Provide the mechanism for de-protection of
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Unformatted text preview: N-Boc valine (below). When H 2 SO 4 is used in place of HBr in Boc de-protection reactions, 2-methylpropene is observed instead of 2-bromo-2-methylpropane. Explain with a partial mechanism. An amino acid can readily be converted into an N-acetyl amino acid using acetic anhydride. Why is this not a viable alternative to Boc or Cbz protection for peptide synthesis? N H OH O O O HBr H 3 N OH O + CO 2 + Br H 3 N O O O O O N H OH O O NEt 3 (as a base) 1. 2. H 3 O +...
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PS Session 7 09.30.10 - N-Boc valine (below). When H 2 SO 4...

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