Conformations of the pyranoid sugars.II. Infrared absorption spectra of some aldopyranosides

Abstract

The co nform ation s of t wen ty-four aldopyranos id es h a ve been st udi ed by a nal ys is of t he ij· infra red absorpt ion spectra. The m ost stable co nform ations of t wel ve of t he glycos id es h ad p reviollsly been assig ned by R ee ves from a st ud y of t heir in stabilit y fa ctors; these conformations wer e aSS lim ed t o apply t o t he cr ystalline state, for whi ch t h e s pec tra h a d bee n recorded . The compounds were classifi ed in to (a) co nfi gurationally an d (b) structurally r elated .gro ups, a nd. t he spectra were in tercompared . The an alys is r evealed grou ps of absor pt lOll ba nds whi ch sh owed a co ncerted shift on chan ge of a nomeri c di spos it ion.Wi t h t hese groups of absorp tion bands t hus ident ifi ed , in tercompa ri son wit ll n ine of t he rem ain ing sp ectra afford ed evidence t hat t he a nomer ic group (1) Tlu·ee of t he glyeosides were ava il a bl e as t heir cr ystallin e complexes with calciu m chl oride. The spectra of t he e complexes were also exam in ed, a nd t he efTect of co-c rystalli zat io n with ca lciu m chlorid e is pointed out . I. Scope and Purpose of the ProjectThe sh ape or conformation of <1, molec ul e gret1.tly influ en ces its rfLtes of refLction fLnd othe r prop er ties. For this reaso n, detailed kn owledge of the co nforme1.-t ions of py nwoid derivfLtiv es is des irable. Our prior pu blir.ations on th is s u bj cct heLVe pres en ted fL system for nnmin g th e co nformat ions of pymnoid compounds [1,2].1 Th e con fo rmfLt ions of num er ous m eth yl glycosides and ot her p,rmnoid deriv;1.tiv es hav e b een determin ed by R eeves from (a) a studv of ster eomeri c fe1.cto rs and (b ) t he ty pe of com plex· formed in cuprHmmon ia solu tion. R eaction of c upnunmo nia with an aldopyranosid e m,1.Y somet imes CfLuse tlltemtion in the co nformation . H ence, e1.ssignments of conformation based on th e formation of copper complexes n eed confirm atioJl bv measuremen t of at least one relevant ph~Ts i cal cJl tll"acteristic.The work h er ein reported was primarily und ertaken to provid e infrared spectrograms of ald osides havin g the p~rmnoid rin g, wit h the obj ect of discovering correh1.tion s that migh t be of value in conformationa l a nalys is. Jt seemed possible that the axial 01' equa torial di sposition of refer ence groups in the various llJolecules of glycop~Tra nos id es should give rise to differ ent v ibrations, and that it should, accor d in gly, b e feasible to identify cer tain b a nds in their sp ectm as being ch aracter istic of t h e different ways of arrnnging t he refer ence groups. The infrared spectra for 11. group of aldopyranosid es have, th ere- Lhe table. 239 fore , b een recorded , ewd the b a nds h ave been compiled a nd then stud ied b\" statistic;1.1 a.nci comp~l,mti ve meth ods .Prior publica tion s from om laboratol".\' on rehted topics have dealt wi t h th e infrared a b orption sp ectrn of sugn,1" }1.Cete1 tes [3] a,nd of some cycli c a ce tals of s ug,(1" [4], e1.nd with a s.\'s tem fo r classif.vin g ...

Infrared spectroscopy of carbohydrates :

“…Then, the spectra (recorded under like conditions) of a large number of compounds having this group are examined, to find out which bands the spectra have in common. For example, the spectra of 24 acetylated glycosides were studied [18], together with those for 21" nonacetylated glycosides [12].…”

“…aldopyranosides [12] showed interaction with the pelleting halide, and six of 27 free sugars [13] gave spectrograms that were different in Nujol and in potassium iodide.…”

Infrared Spectra of Cellulose and its Derivatives

“…Urbanski and his colleagues [129] used the Nujol emulsion method to obtain the spectra of nine mono-, di-, and trisaccharides, isolated by crystallization from water, but it was not possible to separate the anomers. Tipson and Isbell [130] proposed a classification of saccharide derivatives, based on a structural criterion, and obtained the spectra of 24 aldopyranosides with a partial and provisional interpretation of the spectral frequencies; they attributed absorption bands in the 1235-1267 cm-1 region to C-O stretching vibrations, but it will be seen below that this is incorrect. Tipson and his co-workers [131] also studied a large number of infrared spectra of cyclic saccharose acetals, aldopyranosides, and their aceta-derivatives in the region 250-5000 cm-1 .…”

The structure and chemistry of sulfatides

“…A fl-configuration is generally attributed to the glycosidic linkage in cerebrosides. The proof given is based on their hydrolysis by fl-galactosidase (42), on the presence in the IR spectrum of a peak at 11.22 t~ (43) also found in the spectrum of simpler fl-galactosides (44,45), and on their synthesis by a K5nigs-Knorr type of condensation which usually yields the fi-anomer (46). Contradictory results have been obtained, however, by their hydrolysis with ~-galaetosidase (47,48).…”