A new trehazolin analogue, 1-thiatrehazolin, has been synthesized from carbohydrate precursors by a highly efficient route based on our previously developed ketone/oxime ether reductive carbocyclization reaction for the construction of the cyclitol ring and an intramolecular nucleophilic displacement reaction for the construction of the thiazoline ring. 1-Thiatrehazolin is a very potent, slow, tight-binding trehalase inhibitor. A structural model for trehalase inhibition by trehazolin and its analogues, based on the experimental results and supported by theoretical calculations, is proposed.