Abstract O-[2, 2-Bis (alkylthio) ethyl] glycoaldehydes (1a–e; alkyl= Et, Pr, Pr i, Bu t, and-CH 2- , respectively) have been prepared from the corresponding O-[2, 2-bis (alkylthio) ethyl] glycolaldehyde dimethyl acetals (2a–e) by acid hydrolysis. In anhydrous 1, 4-dioxane in the presence of BF 3·(Et 2 O) 2, 1a–c were partially transformed into glycolaldehyde bis (dialkyl dithioacetals), 1d afforded trans-2, 6-bis (tert-butylthio)-1, 4-dioxane and 3, 5-bis (tert- ...