CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 



145 



o — 



MeO OMe 

 I I 

 CH-CH-CH-CH-CH,-OMe 



^N N 



MeHN ^^ 



2',3',5',iV''-Tetramethyiadenosine 



MeO OMe 



I I 



HO,C-CH-CH-UOoH 



weso-Dimethoxysuccinic acid 



O 



MeO OMe 

 I I 

 HO-CH-CH-CHCH-CHj-OMe 



2,3,5-Tnmethyl- D-ribofuranose 



O — 



MeO OMe 

 I I 

 CO-CH-CH-CH-CH,-OMe 



2,3,5-Trimelliyl-D-ribonolactone 



The ring structure of the ribose residue in the pyrnnidine nucleosides has 

 been determined in much the same way. Hydrogenation of triacetyl- 

 uridine gives the 4,5-dihydro derivative which may be methylated with 

 simulataneous deacetylation, then oxidized with bromine and hydrogen 

 bromide. The product is 2,3,5-trimethyl-7-D-ribonolactone, which may be 

 isolated and identified as before.'*'' Tt follows that uridine and cytidine are 

 furanosides. 



The furanose configuration of ribonucleosides is supported by their be- 

 havior towards trityl chloride. It is known that this reagent reacts prefer- 

 entially with primary hydroxyl groups in sugars and their derivatives, 

 giving trityl ethers. Exceptions to the rule are known, Init inider con- 

 trolled conchtions reaction is indicative of the presence of a primary hy- 

 droxyl group in a sugar. Adenosine gives a mixture of mono- and ditrityl- 

 adenosine under these conditions.*^"^® Monotrityladenosine gives a tritosyl 

 derivative which is converted into tritosyladenosine by short acid hydroly- 

 sis. None of the tosyl groups in this compound is replaceable by iodine when 

 heated with sodium iodide. Since this replacement is usually confined to 

 tosyl esters of primary alcohols it follows that tritosyladenosine bears an 

 unsubstituted primary hydroxyl group, i.e., it must be A^®, 2', 3 '-tritosyl- 

 adenosine. The monotrityladenosine must be 5'-monotrityladenosine and 

 consequently adenosine must contain a furanose ring. The ditrityladenosine 

 is iY^,5'-ditrityladenosine, as shown by transformations on its diacetyl 

 derivative. Hydrolysis of the last-named compound with acetic acid yields 

 a diacetyladenosine (2',3'-diacetyladenosine), identical with that obtained 

 by hydrolysis of A*^,2' ,3'-triacetyl-5'-trityladenosine. 



'2 p. A. Levene and R. S. Tipson, J. Biol. Chcm. 101, 529 (1933). 



33 H. Bredereck, Ber. 66, 198 (1933). 



"H. Bredereck, Z. physiol. Chem. 223, 61 (1934). 



" H. Bredereck, Ber. 65, 1830 (1932). 



36 P. A. Levene and R. S. Tipson, J. Biol. Chem. 121, 131 (1937). 



