| 摘要 |
<p>A process for preparing (4S,5R)-2,4-diphenyloxazoline-4,5- dihydro-5-carboxylic acid of the formula (I) by ozonizing (4S,5S)-2,4-diphenyl-5-vinyl-4,5-dihydrooxazoline to give ozonide in situ and subsequent treatment thereof with another oxidizing agent to obtain the required acid. Enantioselective preparation of (4S,5R)-2,4-diphenyloxazoline-4,5-dihydro-5-carboxylic acid of the formula (I) from (S)-(+)-phenylglycine is carried out in such a manner that (S)-(+)-phenylglycine is first subjected to esterification with methanol, a benzoyl or tert-butoxycarbonyl group is introduced with subsequent reduction thereof to give an aldehyde that reacts in situ with vinyl magnesium bromide, the tert-butoxycarbonyl group is removed and using triethylorthobenzoate the 5-vinyl-2,4-diphenyl-4,5-dihydro- oxazoline derivative is prepared (optionally this derivative can be prepared by dehydrating of benzoyl-protected product). By the treatment of the obtained derivative with ozone and subsequent oxidation of the in situ obtained aldehyde, a final product i.e. the (4S,5R)-2,4-diphenyl-4,5-dihydro-oxazoline-5-carboxylic acid is obtained.</p> |
