The extracellular polysaccharides produced by Cryptococczrs lazrrenlii have been isolated and shown to consist of (A) a n acidic polysaccharide containing D-mannose, D-xylose, and D-glucuronic acid; ( B ) a neutral polysaccharide containing D-glucose only.Preliminary structural studies on the acidic material suggest that it consists of a mannosecontaining backbone with xylose and glucuronic acid as end groups, \vhile the glucan contains 1 -,3 3, 1 --t 4, 1 --t 2, and (or) 1 --t 6 linked residues. INTRODUCTION l/Iucli is l t n o~~~n about the origin of sugars fouiid in ho~~~opolysaccharides (1-11). On the other halid the origin of sugars in heteropolysaccharides has not been investigated to any great extent (12, 13).As part of a program for iiivestigatiiig the biosynthesis of monosaccliarides found in heteropolysaccl~arides, we have studied the extracellular polysaccharide produced by the yeast orgallisill Cryptococc~ls lar~rentii.This organism, 1;indly supplied by the United States Department of Agriculture, Peoria, Illinois, was chosen because it produced high yields of polysaccharides froin a wide variety of sugar substances.Cryfltococc~~s laz~rentii \\.as grown 011 an unbuffered casaiiiiiio acids -salts medium n~i t h glucose as the main carbon source (14). An acidic and a neutral polysaccharide were isolated by the follo\\~ing procedure, which was considered unlil

The osymercuration of norbornenes has been found to be acid-catalyzed, and to give oxymercurials which have a higher dipole moment and greater stability toward deosymercuration than do their diastercomers in which the configuration of the mercuri linkage has been inverted. Since these properties can be correlated with those of the osymercurials from norbornenedicarbosylic acids (partly published heretofore and elaborated in the present report) the configurations of which are Icnown, it follo\\~s that the configurations of the osyrnercurials from norbornene are TL (trans). But these configurations must be opposite to those of the osymercurials from cyclohexene, cyclopentene, a-terpineol, and the geoisomeric stilbenes, the formations of which are not acid-catalyzed and the dipole moments of which are lower than those of the diastereomers inverted with respect to the m c r c~~r i linkage. The configuration of these oxymercurials must beLL (cis) and the mechanism of their formation l n~~s t be different from the acid-catalyzed oxyrnercuration of norbornene. The mechanism for cis (LL) addition has previously been s~tggested as non-ionic. Calculation of the electric moments of these JJ diastereomers shows that hindrance to group rotation must prevail. I t is reasonable to attribute the relative ease with which they may be d e o s y~n e r c~~r a t e d to this hindrance.For some years there has been a difference of opinioil in respect of the mechanism whereby the elements of hydroxy-or alkoxy-mercuric salts add to allcenes. This controversy is of interest beyond that of the oxyinercurials because oxymercuration may provide an insight of alkene reactions not provided by less definitive reactions of these hydrocarbons. Thus it has been observed that oxymercuration is generally entirely stereospecific, with simple second-order kinetics in which a cis-geometric isomer is oxymercurated a t a faster rate than is its trans-modification. However, iloile of these characteristics define the mechanism of reaction.In 1935 the reaction was specified as an addition of molecular hydroxy-or allcoxymercuric acetate to the carbon-carbon double bond ( I ) , and this belief that the added groups were in contiguous (so-called cis) configuration was reiterated in 1947 (2). Meanwhile, the alternative postulation has been made (3) that an ionized allane-mercurinium salt is first formed from an ionizable mercuric salt and an alkene. The cation of this salt is subsequently attacked by a nucleophilic hydroxide or alkoxide ion, with inversion, to produce the oxymercurial in which the added groups are in the non-contiguous (socalled trans) relationship to one another. This inechanism is portrayed here for the oxymercuration of 1,4-methylene-A2-cyclohexene (norbornene, I).I t might be predicted from this mechanism that the reaction would be favored by a system in which the ionization of mercuric salts would be enhanced. Moreover, the prevalence of the two possible products, 3-J-methoxy-l,4-TT-inethylenecyclohexyl-2-Tmercuric salt (IV) versus...

A chemical procedure for the determination of the labelling in the terminal carbon atoms of some unsubstituted carbohydrates using 20 mg of material is described. The procedure has been tested on D -g l u~~~e -l -C~' , ~-glucose-6-C'~, D -~~u c o s~-~-C " , and D-glucuronolactone-6-CI4 with satisfactory results.A procedure based on the work of Smith el al. for the degradation of hesoses via the methyl glucopyranosides is described and has been applied to D-glucose-1-C14 and ~-glucose-6-C'4 with satisfactory results. These procedures have been designed to give barium carbonate as the final product in each determination. INTRODUCTIONThere are many procedures for determining CL4 distributioil in carbohydrates described in the literature (1-I&), but of these oilly two afford a conlplete determination of the labelliilg on a nlillimole scale (11, 13). The renzainder either require large amounts of material or do not give the labelliilg in all of the carbon atoms. Guilsalus and Gibbs have described a fermentation procedure with Le~iconosfoc mesenteroide~ (11) for the degradation of glucose and Altermatt, Blacl;wood, and Neish (12) have extended the method to the degradation of xylose. Although this procedure yields satisfactor!. results it is limited to those sugars which the organisin lvill fernzent. Boothroyd, Brolvn, Thorn, and Neish have described chemical procedures for the deter~nillatioll of the C1" labelling in glucose (13) and xylose (14) (see also 10). This method is applicable to inally sugars.A lilnitation to the methods available for radioactive degradation procedures is the type of counting apparatus available. If counting of bariuin carbonate plates is the only method available then the combustion of large molecules, such as dimedone and phenylhydrazone derivatives, is not always suitable, since the labelled moiety beconles diluted with large quantities of unlabelled carbon material.The first part of this paper describes a q net hod by which the CL4 labelling in the terlninal positioil of any unsubstituted carbohydrate may be determined on a lniniinurn of inaterial (20 ing). This quantity is the amount required to give 30 mg of barium carbonate for each of the three determinations involved.The sodiu~n inetaperiodate oxidation of sugars has (16, 17) been extensively studied in this (15) and other laboratories. It has been shown that colnplete oxidation of an aldohexose to 5 inoles of formic acid (C 1-5) and 1 lnole of fornlaldehyde (C-6) talies place rapidly at pH 8.0 (15) (phosphate buffer). I-Iough et al. (17) have shown that the oxidation of glucuronic acid proceeds sinoothly to give 1 inole of carbon dioxide (C-6) and 5 ~noles of for~nic (C 1-5) a t p1-I 3.6 (acetate buffer). The borohydride reduction of oligosaccharides and subsequent metaperiodate oxidation carried out in sit11 without isolatioil of the intermediatory glycitol derivative has been studied (18). These methods \vhen applied to inonosaccl~arides gave a method for determining the labelling in the terininal carbon atoms.The speci...

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Methods which might be used in the chemical degradation of carbon-14-labelled carbohydrates required an investigation of the reaction of sodiuln lnetaperiodate 117ith certain nitrogen-containing carbohydrate derivatives. The aim of these experiments was to convert specific carbon atoms of the carbohydrates to forinic acid, which coulcl then be oxidized to carbon dioxide with mercuric acetate. The carbon dioxide \\-as then converted to barium carbonate and its activity determined.The oxidation of phenylosazones (1) and pheilylosotriazoles (2) by sodium metaperiodate resulted in the rapid consuinptioll of the theoretical quantity of metaperiodate. This was followed, in the case of the phenylosazones, by a slow overoxidation by the metaperiodate. Recently the inetaperiodate oxidation of some pl~enylhydrazones has been reported by O'Donnel and Percival (3), who found that the consuinption of oxidant corresponded to the amount required for an acyclic structure. They did not deterlnine the quantities of formaldehyde and forinic acid produced during the oxidation.D-Mannose phenylhydrazone and D-xylose 2,4-dinitro-phenylhydrazone have been oxidized with sodium inetaperiodate in aqueous ethanol; the inetaperiodate consumed, the forinic acid and forinaldehyde produced were then measured.