Reduction of methyl hydrogen di-O-acetyl-dextro-tartrate (I) with sodium borohydride in water afforded l-threono-γ-lactone (II). l-Threose (IV) was obtained on treatment of the γ-lactone (II) with an excess of disiamylborane. Reduction of ester chloride of di-O-acetyl-dextro-tartaric acid (VI) with tri-n-butyltin hydride yielded methyl di-O-acetyl-l-threuronate (VII). Attempts to reduce 2-deoxy-pentarate ester (X) derived from ester chloride (VI) via diazoketone (VIII) with sodium borohydride to give 2-deoxy-threo-pentono-γ-lactone (XI) gave unsatisfactory results. Formation of methyl l-threo-2,3-di-O-acetyl-5-chloro-5-deoxy-4-C-hydroxymethyl-4,4′-anhydropentonate (IX) in addition to diazoketone (VIII) was observed when ester chloride (VI) was treated with an excess of diazomethane. On the basis of the observed (−)-Cotton effect in the 290 nm region of ORD and CD spectra of l-threose (IV) and d-erythrose, possibility of the presence of an open chain non-hydrated alde-hyde-form of aldotetrose in water was discussed.

Reduktion des Tartrats (Ia) und nachfolgende Hydrolyse liefern das Lacton (II), das mit überschüssigem Disiamylboran und durch anschließende Hydrolys L‐Threose (III) ergibt.