合成路线1

1) The reaction of 3-(2,5,5-trimethyl-1,3-dioxan-2-yl)thiophene (I) with butyllithium, SO2 and hydroxylamine-O-sulfonic acid in hexane/THF gives the corresponding sulfonamide (II), which is hydrolyzed with HCl yielding 3-acetylthiophene-2-sulfonamide (III). The cyclization of (III) with pyridinium bromide perbromide (IV) and NaBH4 affords 4-hydroxy-3,4-dihydro-2H-thieno[3,2-e][1,2]thiazine 1,1-dioxide (V), which is treated with 1,3-dibromopropane (VI) and NaH in DMF giving the corresponding 3-bromopropyl derivative (VII). The protection of the hydroxy group of (VII) with ethyl vinyl ether (VIII) in p-toluenesulfonic acid yields the ethoxyethyl ether (IX), which by reaction with sodium methoxide in refluxing methanol affords the 3-methoxypropyl derivative (X). The sulfonation of (X) with butyllithium, SO2 and hydroxylamine-O-sulfonic acid in hexane/THF gives the sulfonamide (XI), which is oxidized with CrO3/H2SO4 to yield 2-(3-methoxypropyl)-4-oxo-3,4-dihydro-2H-thieno[3,2-e][1,2]thiazine-6-sulfonamide 1,1-dioxide (XII). The stereocontrolled reduction of (XII) with (+)-beta-chlorodiisopinocamphenylborane [(+)-CDPB] in THF affords the 4(S)-hydroxy derivative (XIII), which is finally treated first with p-toluenesulfonyl chloride/triethylamine and then with ethylamine in THF.