A procedure is developed for the 'one-pot' acylation and methylation of isoxazolines at C(4). Thus the 5-substituted isoxazolines (8), (9), and (18) were converted into their cis -4-methoxycarbonyl- trans -4-methyl derivatives (10), (11), and (19), by deprotonotion using lithium diisopropylamide, followed by the sequential addition of methyl chlorofonmate and methyl iodide. The reduction of these substituted isoxazolines was then investigated. N -Methylation using Meerwein's salt, and reduction of the derived N -methylisoxazolinium salt using sodium borohydride gave isoxazolidines (14) and (20), but only in modest yields. The analogous N -methylation - reduction of the lactone-isoxazoline (12) was not stereoselective. The isoxazolidines (14) and (20) have the correct relative configurations at C(3) and C(4) for conversion into lankacidin analogues.