VOL. 12 (1953) DEGRADATION OF ALDOSES 205 



hoped therefore that the method can be perfected so as to permit the degradation of the 

 hexuronic acids to the corresponding penturonic acids. The physical and chemical prop- 

 erties of the latter having been ascertained, a search for these interesting compounds 

 in nature might be successful. 



The present authors wish to gratefully acknowledge that they were prompted to 

 reinvestigate the degradation of the ^^wacetylated sugar disulfones by observations made 

 in our laboratory by Prof. Elvin A. K.abat*. He was able to prepare the hitherto un- 

 obtainable disulfone derived from D,L-glyceraldehyde^^ by treating D,L-glyceraldehyde 

 diethyl mercaptal with perpropionic acid in an anhydrous medium. This disulfone when 

 treated with cold aqueous ammonia readily decomposed into bis (ethanesulfonyl)- 

 methane and, most probably, glycolic aldehyde, but the latter compound has not yet 

 been identified. Dr Kabat and the present authors plan to report about this at a later 

 date. 



EXPERIMENTAL 



D-arahinose from D-mannose diethyl mercaptal 



Two g of D-mannose diethyl mercaptal^^ were dissolved by warming in 40 ml of purified dioxane^^, 

 the solution was cooled somewhat and distilled perpropionic acid^* was added (15% excess over the 

 required four moles). The solution became quite warm and within a few minutes the crystalline 

 disulfone began to precipitate from solution. After 5 minutes, the mixture was placed in ice for a 

 further 14 hour, then filtered and washed with cold dioxane to yield 2.20 g (90%) of the disulfone. 



The crude disulfone was mixed with 40 ml of water and to the slurry there was added one drop 

 of concentrated aqueous ammonia. Within a minute the precipitation of bis (ethanesulfonyl) methane 

 was observable. After y, hour at room temperature, the mixture was extracted four times with 20-ml 

 portions of chloroform, and the aqueous layer was concentrated at reduced pressure (bath temperature 

 below 55°). Final concentration in a vacuum over at 40° C, was followed by addition of methanol and 

 crystallization at +4° C. In a typical experiment there was obtained 0.87 g of D-arabinose (83% 

 based on the mercaptal) having [a]jf = — 102.8° (equilibrium, C, 4, water). 



The chloroform extracts were dried (sodium sulfate) and concentrated at reduced pressure to 

 give 1.09 g (78%) of bis (ethanesulfonyl) methane, which melted at 101-103° after recrystallization 

 from water. A mixed melting point with authentic bis (ethanesulfonyl) methane was undepressed. 



SUMMARY 



A simple procedure is described for the degradation of hexoses to pentoses in excellent yields. 

 The method involves oxidation of the hexose mercaptal to the disulfone, followed by treatment with 

 very dilute aqueous ammonia, to give the pentose and bis(ethanesulfonyl)methane. 



RfiSUM:^ 



Une methode simple pour la degradation de hexoses aux pentoses a haut rapport est decrite. 

 Ladite methode utilise I'oxidation du mercaptal de I'hexose au disulfone, suivi par traitement avec 

 une solution d'ammoniac aqueuse tres diluee, donnant le pentose et le bis(ethanesulfonile)methane. 



ZUSAMMENFASSUNG 



Es wird eine einfache Methode beschrieben, um Hexosen zu Pentosen in gute Ausbeute ab- 

 zubauen. Zuerst wird das Merkaptal der Hexose zu dem entsprechenden Disulphon oxydiert. Das 

 Disulphon zerfallt bei der Behandlung mit sehr verdtinntem wassrigen Ammoniak in die nachstnie- 

 drige Pentose und Bis(ethansulphonyl) methane. 



* On sabbatical leave in Berkeley from Columbia University, winter 1952-53. 

 References p. 206. 



