The effects of water activity, salt, sodium metabisulphite and Embanox-6 on the stability of carotenoids in dehydrated carrots has been investigated. Carotenoid pigments have been found to be most stable at 0.43 a,. Incorporation of salt, sodium metabisulphite and Embanox-6 significantly reduced the rate of carotenoid destruction and non-enzymic browning in dehydrated carrots.

Heating 5'-O-acetyl-2'-O-toluene-~-sulphonyluridine (I) with either sodium azide in methyl cyanide or sodium acetate in acetonylacetone affords 5'-0-acetyl-02 : 2'-cyclouridine (11; R = H, R' = Ac). The latter is converted into 5'-O-acetyl-2'-deoxy-2'-iodouridine (111) by sodium iodide in acetonylacetone containing glacial acetic acid ; the iodide (111) , also obtained directly from sulphonyl derivative (I) with sodium iodide, is now assigned the ribo-configuration.3' : 5'-Di-O-acetyl-0 : 2'-cycZouridine on acid hydrolysis gives both uridine and spongouridine, in contrast to O2 : 2'-cycZouridine which gives only the latter. The chemistry of the oxazolidine ring in cyclouridine derivatives is discussed and a possible pathway is suggested for the biochemical conversion of pyrimidine ribo-into deoxyribo-nucleosides.

Effect of processing temperature on the changes in free nucleotides, nucleosides and bases in goat and sheep meats was investigated. The major changes in nucleotides and related compounds took place during first 30 min of heating and the rates of changes were maximum at 60 degrees C and minimum at 100 degrees C. At 120 degrees C, thermal degradation of inosinic acid proceeds at significant rates but below 100 degrees C major changes are brought about by phosphomonoesterases (5'-mononucleotidases) during initial stages of heating.

By D. M. BROWN, D. B. PARIHAR, C. B. REESE, and SIR ALEXANDER TODD. 5'-O-Acetyl-2'-O-toluene-fi-sulphonyluridine reacts with sodium iodide in hot acetonylacetone, to give 5'-O-acetyl-2'-deoxy-2'-iodouridine from which by hydrogenation and deacetylation 2'-deoxyuridine is obtained. The same route starting from 5'-O-acetyl-3-P-~-ribofuranosylthymine leads to thymidine. The synthetic deoxyribonucleosides are identical with the naturally occurring compounds.

By D. M. BROWN, D. B. PARIHAR, SIR ALEXANDER TODD, and S. VARADARAJAN.2' : 3'-O-isoPropylidene-O2 : 5'-cycZouridine and 2' : 3'-O-isopropylidene-5'-O-toluene-p-sulphonyluridine both react with sodium ethyl sulphide to give 5'-deoxy-5'-ethylthio-2' : 3'-O-isopropylideneuridine. The same reaction applied to O2 : 2'-cycZouridine affords 3'-deoxy-3'-ethylthiouridine from which 3'-deoxyuridine is obtained by treatment with Raney nickel.2' : 3'-O-isoPropylidene-0 * : 5'-cycZouridine with hydrogen sulphide and triethylamine gives 2' : 3'-O-isopropylidene-Z-thiouridine from which 2-thiouridine can be obtained. The thiolation reaction also affords polysulphides of the probable structure R-S,,-R where n = 1, 2, or 3, and R is an isopropylidene-2-deoxy-2-uridinyl residue.