4. Below you find the molecular structure of cephalexin. Its specific rotation is [α] = +149.3°.
II
CgHCHCNH
NH2
CH3 COH
cephalexin
A) Is cephalexin optically active? Answer with yes or no. If your answer is yes, is cephalexin levo- or dextrorotatory? (Total 2 points)
B) Label the chiral centers of cephalexin with R or S. Note: Assume that the hydrogen of each chiral center points backwards for your labeling. (Total 3 points)
C) By using only R and S, state the sequence of R and S that would represent an enantiomer, diastereomer, and epimer to cephalexin. (Total 4 points)
R/S sequence of cephalexin:
R/S sequence of the enantiomer to cephalexin:
R/S sequence of a diastereomer to cephalexin:
R/S sequence of an epimer to cephalexin:
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