Reduction of the keto group of 5-delta-methylene pristinamycin IA (I) by means of NaBH4 in the presence of CeCl3 provided the allyl alcohol (II). Subsequent chlorination of (II) with SOCl2, furnished a mixture of compounds containing the 5-delta-(chloromethyl) (III) and the 5-gamma-chloro-5-delta-methylene (IV) derivatives. Treatment of the crude mixture with morpholine (V) in refluxing acetonitrile yielded the title 5-delta-morpholinomethyl analogue.
In an alternative method, Michael addition of morpholine (V) to the unsaturated ketone (I) gave adduct (VI). Subsequent ketone reduction in (VI) with NaBH4 provided the corresponding alcohol (VII) as a diastereomeric mixture. Dehydration of alcohol (VII), upon treatment with diethylaminosulfur trifluoride, then yielded the title compound.