( 779 ) 



Chemistry. Prof. f'. A. li()BR\ dk liinvN pi-esciils conuniniicalioM 

 N". 8 on iiili-jiiiioieciilar roai-r.-iiioonioiits : C L. JrNGius. "T/ie 

 iiHifiKf/ h'tnisfoi-iinitioii of the liro^) .stfrcoisinin'ric pfntwi'tntcs 

 of d-qhicosf.'^ 



(Communicated in tlie meeting of Marcli lit. I90i\ 



1. It is well known that tlie esterification of alcohols by means 

 of' acetic anhydride is accelerated in a high degree bv the presence 

 of catalyzers and this of conrse also applies to the sugars. But it 

 is a rcmarkal)le fact that in the case of these polyhydric alcohols 

 we arrive at Aarious isomeric pentacelates according to the natui-e 

 of the catalyzer. The investigations of Franchimont ') and of Hkrzfkld ') 

 liave shown that, when dry sodiumacetate is used as catalyzer, we 

 obtain a product melting at 134" (,i), whilst according to Erwig and 

 KöNiGS ■') treatment with ZnCl^ yields a product melting at 112" («)• 

 After Franchimoxt had proved (hat these two compounds were in 

 reality isomeric*) [the first was formerly thought to be a diglucose- 

 octacetate] this chemist supported the view that they may be best 

 represented as derived from the so-called oxide-form of glucose "). 

 The two pentacetates will then be stereoisomers as the oxide-form 

 of glucose, which contains one asymmetric carbon atom more than 

 the aldehyde-form, must give rise to two isomers. 



As in the case of the tAvo niethylglucosidcs ") we arrive, on apj)lying 

 Tollens' glucose fornnda, at the following constitution of the 

 pentacetates : 



AcO — CH ^ CHOAc — CHO Ac — CH — CHOAc — CH.OAc ') 



1 ' 



The existence of two isomers is explained by the fact that the 

 terminal C-atom on the left appears as a new asymmetric atom. 



2. It was known that the ,-?-isomor formed bv sodiumacetate is 



1) A few yeais ago, Tanret described a Uiiiil isomeric glucosepentacelate 

 m.p. 8(3' (Bull. 13. 2G1 (1895). My investigation has led mo to tlie conclusion 

 that this isomer does not exist but is a mixture of the other two. 



2) Ber. 12. 1940. 



3) Ber. 13. ^2(^:^. 

 *) Ber. 22. 1464. 



■') Recueil. 11. 106 (1892) Recueil. 12. 310. 

 Ö) These Proc. June 24 1893. 

 ') E. Fischer B. 26. 2400 (1893). 

 8) Ac =• CH3 — GO. 



