Short synthesis of 5,6-dihydro-(S)-4-(ethylamino)-(S)-6-[C.sup.3 H.sub.3 ]-4[2,3-b]thiopyran-2-sulfonamide 7,7-dioxide and related non radioactive compounds

A process for the preparation of a Compound of structural formula I:

• ##STR4## and its hydrochloride salt wherein R is C.sup.1 -C.sup.3 alkyl and R.sup.1 is C.sup.1 -C.sup.3 alkyl or a radio-labeled C.sup.1 -C.sup.3, which comprises the steps of:
• A) protecting the nitrogen substituents of a compound of structual formula II ##STR5## by treating the compound of structual formula II with an excess of a blocking agent from about 4 eq to about 8 eq, belonging to a group consisting of di-t-butyl dicarbonate, or carbobenzyloxy chloride or in the presence of from about 2 eq to about 3 eq (each) Et.sub.3 N/DMAP to form a compound of structural formula HI:
• ##STR6## B) methylating the compound of structural formula III at the C-6 position, treating the compound of structural formula III with an excess of a base, from about 2.0 eq to about 3.0 eq, selected from the group consisting of lithium bis(trimethylsilyl)amide, n-butyl lithium, tert-butyl lithium, or lithium diisopropylamide in the presence of an anhydrous solvent selected from the group consisting of THF, ether, or dioxane, and adding from about 0.5 eq to about 1.5 eq of methyl iodide in the presence of an anhydrous THF to form a compound of Structural formula IV:
• ##STR7## C) deprotecting the nitrogen substituents of the compound of structural formula IV, and purifying and isolating the compound of structural formula I, wherein R and R.sup.1 are as above.