TBR Epimer Clarification

[justadream]

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As I understand it, epimers are a subset of diasteroemers. In particular, epimers are diasteromers that differ in R/S at only one chiral center.

So for TBR Ochem Passage I #2 (pg 221)

"If the side chain chiral center [of isoleucine] were changed [in orientation], the new structure would be____"

Answer: Diasteroemer.

I understand why it's a diasteromer but "epimer of isoleucine" is also an answer. Why isn't it an epimer? Isoleucine has 2 chiral centers so changing just one of them would seem to fit the definition of an epimer.

 

[sillyjoe]

For MCAT purposes, epimers are only a classification for sugars i.e. empirical formula CH2O different at only 1 stereogenic center.

 

[justadream]

Okay great thanks!

 

[justadream]

I remember TPR Orgo saying that anomers were epimers formed from rings.

TBR Ochem says that anomers are epimers where the change is at the ANOMERIC carbon (thus, a change at any other carbon in the ring wouldn't be considered an anomer?).

So is TBR's more restrictive definition of an anomer the correct one for "MCAT purposes"?