Gulonic acid lactone

Concentration in this manner allows sufficient time for the gulonic acid to be converted to the lactone in the presence of a trace of hydrochloric acid. The checkers observed also that an easily crystallized lactone was always obtained if concentration in mcuo were employed. 

N-methyl-l,2-diphenylethylamine, 34, 64 tetraphenylarsonium chloride hydrochloride, 30, 97 Guanidine, 32, 96 Guanidine hydrochloride, 32, 45 Guanylthiourea, 35, 69 D-GuLONIC ACID, y-LACTONE, 36, 38... 

XIII. Biological Role of the Gulono-1,4-lactones and Gulonic Acids.320... 

A short synthesis of D-gulono-1,4-lactone (2) from the inexpensive and readily available D-xylose (34) was first reported by Fischer and Stahel,18 and subsequently by others,12,25-31 and is shown in Scheme 6. The addition of hydrogen cyanide to D-xylose (34) resulted in the formation of cyanohydrins 35 and 36 which, on hydrolysis, afforded a mixture of D-gulonic acid (4) and D-idonic acid (37). D-Gulono-1,4-lactone may be obtained in 30-33% yield by recrystallization of the reaction products. In a similar way, L-xylose (l-34) has been converted32,33 in high yield into a mixture of L-gulonic and L-idonic acids. 

Several amides of derivatives of L-gulonic acid (3) have been prepared. On treatment of 2,3 5,6-di-O-isopropylidene-L-gulono-l,4-lactone (the preparation of which is discussed in Section V) with ammonia in methanol, 2,3 5,6-di-0-isopropylidene-L-gulonamide (45) is formed.76 Similarly, 3,5-O-benzylidene-L-gulonamide (46) was prepared76 from the corresponding lactone. 

The simple cleavage of lactones 1 or 2 with alcohol and acid has not been reported. However, when 1 is treated with benzaldehyde diethyl acetal and hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (47) is formed in >90% yield.77,78 No other isomers were observed, and other acetals of benzaldehyde, as well as aliphatic aldehydes, afford similar products in good yield.77 D Addieco prepared36 similarly protected derivatives of L-gulonic acid by oxidation of l,3 2,4-di-0-ethylidene-D-glucitol (15), followed by esterification of the resulting acid with diazomethane. 

A variety of miscellaneous derivatives of gulonolactone has been reported. Linn treated D-glucofuranurono-6,3-lactone (7) with chlorobenzene and aluminum trichloride in order to obtain115 6-deoxy-6,6-diphenyl-L-gulonic acid (70). Various related compounds were also prepared. When 7 was treated with sulfur dioxide and 2-(isonicotin-oyl)hydrazine in water, 6-deoxy-6-(2-isonicotinoylhydrazino)-6-sulfo-D-gulono-1,4-lactone (71) was formed in 81% yield.116,117 Kawabata... 

The most important oxidation product of L-gulono-1,4-lactone (I) is, without a doubt, L-ascorbic acid (6 vitamin C), and the most important oxidation product of L-gulonic acid (3) is L-xyZo-2-hexulosonic acid (5), which serves as a key intermediate in the commercial production of L-ascorbic acid. The literature covering the methods by which 1 or 3 (or derivatives thereof) has been converted into 6 or 5, as well as other methods for the preparation of 6, has been reviewed,1 and will not be discussed here. 

Ascorbic acid, which is closely related to the sugars and is no doubt derived from them in the metabolism of the cells of plants, has been shown to be identical with vitamin- C (Szent-Gyorgyi). It has the constitution of a lactone of a-keto-i-gulonic acid (W. N. Haworth, T. Reichstein) ... 

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