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Magazine Chapter 23: Q47P (page 1255)
Without referring to the chapter, draw the chair conformation of
(a) 伪 -D-mannopyranose (the C2 epimer of glucose).
(b) 尾 -D-allopyranose (the C3 epimer of glucose.)
(c) 伪 -D-galactopyranose (the C4 epimer of glucose).
(d) N-formylglucosamine, glucose with C2 oxygen atom replaced by a formylated amino group.
Short Answer
(a) 伪 -D-mannopyranose (the C2 epimer of glucose).
(b) 尾 -D-allopyranose (the C3 epimer of glucose.)
(c) 伪 -D-galactopyranose (the C4 epimer of glucose).
(d) N-formylglucosamine, glucose with C2 oxygen atom replaced by a formylated amino group.
Step by step solution
A concept:
Pyranose is a six membered cyclic hemiacetal. For example, a six membered ring of glucose is known as glucopyranose. Sugars which have the common configuration like the arrangement of -H and -OH around carbon atoms are same except the carbon present at position or carbon number are known as epimers. For example, glucose and mannose are epimers of each other.
(a) α -D-mannopyranose (the C2 epimer of glucose).
A six membered ring of mannose is known as 伪 -D-mannopyranose. The chair conformation of is shown by the figure below.
(b) β -D-allopyranose (the C3 epimer of glucose.)
A six membered ring of allose is known as 尾 -D-allopyranose. The chair conformation of is shown by the figure below.
(c) α -D-galactopyranose (the C4 epimer of glucose).
A six membered ring of galactose is known as 伪 -D-galactopyranose. The chair conformation of is shown by the figure below.
(d) N-formylglucosamine, glucose with C2 oxygen atom replaced by a formylated amino group.
When the C2 oxygen atom of glucose is replaced by a formylated amino group, it forms N-formylglucosamine. The chair conformation of N-formylglucosamine. is shown by the figure below.
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