How do you draw a structural diagram for MSG(monosodium glutamate)?

So what you need to know first is that MSG is the sodium salt of glutamate (= glutamic acid). Next it would be helpful to know that glutamate is an amino acid (a building block of proteins).
The general structure of an amino acid is generally written as
NH2CHCOOH
......|
......R
Each amino acid has a different R group. The R for glutamate is CH2CH2COOH
see Amino acid - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Amino_acid)

So the answer is
NH2CHCOOH
......|
......CH2CH2COOH
Or see … Glutamic acid - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Glutamate)