This compound can be obtained in two related ways: 1) The cyclization of 4-acetamidocyclohexanone (I) with thiourea (II) by means of Br2 in hot acetic acid gives 6-acetamido-2-amino-4,5,6,7-tetrahydrobenzothiazole (III), which by hydrolysis with refluxing aqueous HBr yields racemic 2,6-diamino-4,5,6,7-tetrahydrobenzothiazole (racemic IV). Optical resolution with L-(+)-tartaric acid affords the (S)-(-)-isomer (IV), which is finally treated with propionaldehyde and LiBH4. 2) The reaction of 4-aminocyclohexanol (V) with phthalic anhydride (VI) in toluene gives the phthalimido derivative (VII), which is oxidized with potassium dichromate - H2SO4 to the corresponding cyclohexanone (VIII). The cyclization of (VIII) with thiourea (II) and Br2 as before affords 2-amino-6-phthalimido-4,5,6,7-tetrahydrobenzothiazole (IX), which is deprotected with hydrazine in refluxing ethanol yielding racemic (IV), already obtained.