The stereo configuration of rhamnose. This methyl pentose sugar 

 has been shown by Fischer to have the stereo configuration 



OH H H 

 CH 3 CHOH. C . C . C . COH, but he was unable to obtain 



H OH OH 



any data which would establish the stereo structure of the first 

 group CH 3 CHOH. This physico-chemical method for establishing 

 the structure of the sugars can be applied in this case where the 

 usual strictly chemical methods fail. Writing the carbon chain for 



rcH 3 c.c.c.c.cn . . 



rhamnose |^ (1) (2) . (3) (4) (5) J, and referring to 



the following cyanid syntheses, methyl tetrose > rhamnose > rham- 

 nohexose > rhamnoheptose, the specific rotations of the corresponding 

 lactones having been found by Fischer to be methyl tetronic 47, 

 rhamnonic - 35, rhamnohexonic + 84, and rhamnoheptonic + 56, it is 

 seen that the hydrogen atom is to be placed above carbons 3 and 4 

 and below 1 and 2, yielding the following configuration for rhamnose, 



OH OH H H 

 CH 3 . C . C . C . C . COH. This agrees with Fischer's 



H H H H 



structure for the atoms 2, 3, and 4, and it also shows the configura- 

 tion of atom 1, which has been in doubt. Rhamnose is thus a 

 reduction product from 1-mannose. It is interesting to note that 

 Winther a has previously selected this configuration for the first 

 carbon, basing his selection upon the fact that Tate's bacillus 

 attacks rhamnose. 



Partial stereo configurations of rhodeose and fucose. The methyl 

 pentose rhodeose yields a lactone with the specific rotation 76, 6 

 consequently its structure can be partially determined from the 



I OH | 



above principles to be CH, . C . C . C . C . COH, and 



I H | ] 



it follows that its antipode, fucose, is the mirror image of this. 



PROOF OF THE POSITION OF THE LACTONIC RING. 



F 



The foregoing relations furnish a proof of a view which organic 

 chemists have been led to adopt by a large number of chemical facts, 

 namely, that the formation of lactones involves the ^-carbon atom 

 preferably to any other. The parallel relation between the position 

 of the lactonic ring and the sign of the rotation of the lactone is 

 based on the assumption that the ring is formed on the ^-carbon 

 atom; if it were considered as formed on any other atom whatso- 

 ever the parallelism would no longer hold even approximately; thus, 

 referring back to Table 2, if the ring is supposed to form on the 



[Cir. 49] 



oBer. d. chem. Ges., 1895, 28: 3000. 



& Votocek, Zts. Zucker-Ind., (Bohmen.) 1902, 25: 297. 



