Iminazoline mutarotation

To ascertain the presence of asymmetric transformation, mutarota-tion in solution was determined. Figure 12 shows the mutarotation of the above products of alanyl iminazolines in methanol solution. 

Figure 14. Mutarotation of an iminazoline (a) removal from the system by crystallization (b) asymmetric transformation, but no preferential crystallization (c) racemization and (d) no epimerization...

In the mutarotation experiment of iminazoline from alanine and isopropylpropylenediamine, the recovered alanine residue racemized entirely in methanol solution. Why, then, can the iminazoline containing the optically retained amino acid residue be synthesized ... 

Table VI. Results of Mutarotation Experiments Using an Amino Acid and an Iminazoline...

In both instances, the mutarotation velocity with pyrrolidine was faster than with the other amines. When iminazoline synthesis was conducted between alanyliminoether and 2-aminomethylpyrrolidine, excess pyrrolidine in the reaction media probably accelerated the epimerization reaction. Racemization is faster than crystallization of this, diastereomer, which is less soluble than the other diastereomers. In the case of isopropylpropylenediamine, the excess amine racemizes poorly, so the crystallization was faster than the racemization. 

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See also in sourсe #XX -- [ , ]

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