Oxazolines carboxy group protection

The carboxy-group has been protected in lithium aluminium hydride reductions by conversion into 2-oxazolines (639) through acid-catalysed rearrangement of the corresponding aziridine. The carboxylic acid or... 

Ring closure of (3-hydroxy-a-amino acids with sulfuryl chloride/triethylamine 68 is accompanied by formation of (3-chloroalanine,16 1 whereas cyclization of urethane-protected serine and threonine by the Mitsunobu reaction 54 69 70 leads to oxazoline and dehydroalanine formation as side products. 47,71 Formation of dehydroalanine can be prevented by bulky carboxy protecting groups such as tert-butyl esters. 69 ... 

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