A dipeptide, "x" on complete hydrolysis gives "y" and "z". "y" on treatment with aq. produces lactic acid. ​

Question

A dipeptide, "x" on complete hydrolysis gives "y" and "z". "y" on treatment with aq. \(HNO_2\) produces lactic acid. On the other hand "z" on heating gives the following cyclic molecule.

Based on the information given, the dipeptide X is: 

(1) valine-glycine 

(2) alanine-glycine 

(3) valine-leucine 

(4) alanine-alanine

Answer 1

Correct option is: (2) alanine-glycine 

\(NH_2 - \underset{\underset{\underset{\underset{(x)}{\text{alanine - glycine}}}{CH_3}}{|}}{CH} - \underset{\underset{O}{||}}{C} + NH - CH_2 - \underset{\underset{O}{||}}{C} - OH \xrightarrow{\text{Hydrolysis}}\) \(NH_2 - \underset{\underset{CH_3}{|}}{CH} - \underset{\underset{O}{||}}{C} - OH \ (y) + NH_2 + CH_2 - \underset{\underset{O}{||}}{C} - OH \ (z)\)

\(NH_2 - \underset{\underset{\underset{(y)}{CH_3}}{|}}{CH} - \underset{\underset{O}{||}}{C} - OH \xrightarrow{aq. \ NHO_2} HO - \underset{\underset{\underset{\text{Lactic acid}}{CH_3}}{|}}{CH} - \underset{\underset{O}{||}}{C} - OH\)