8 hours after which time it continued to rise reaching final equilibrium after a total of 56 hours. After 20 hours a strong colour was obtained with the arsenophosphotungstic acid reagent and the solution strongly reduced Fehling’s solution.
oj
see 5*1.6.1.5* Fartiîl Hydrolysis of Tri-QisoPropylidene o-Gluoosone Hydrate.
The compound (I) (1.32g.) was dissolved in 85% acetic acid (26ml.) and the solution maintained at 50® for IG hours. The solution was evaporated at 40® to a pale yellow syrup (l.lg.) and residual aoetio aoid was removed by co-distillation under reduced pressure with toluene. The syrup was dissolved in a few ml. of hot methanol and water added to turbidity; a small orystalline fraction (O.lg.), identified as unchanged (I),
separated out and was removed by filtration. The syrup, which gave only a very faint colour with the arsenophosphotungstic aoid reagent and did not reduce Benedict's solution, was
extracted with acetone. The extract was evaporated to a
faintly coloured syrup, soluble in most organic solvents except light petroleum and insoluble in cold water* Attempts to
crystallise it from various solvents met with no success. 6.1.6. Di-O-Acetyl-Di-O-isorropylidene o-Glucosone Hydrate.
The syrup (^.59g*) obtained by partial hydrolysis of the compound (I) was dissolved in acetic anhydride (4.0ml.) and warmed at
75° for 5 hours witu anhydrous sodium acetate (O.lg.). The cooled reaction mixture was worked up as in 6.1.2. b), and the resultant syrup (w.47g.) crystallised from ether-light petroleum, colourless aggretated prisms, (0.38g., 75.0%), m.p. 69°.
Reorystallisation from aqueous methanol gave di-£-aoetyl-di-0- -ieopropylidene o-glucosone hydrate, m.p. 70®, +1 5.9®
(o, 1 .4 4 in methanol) [Found: C, 53.2; H, 6.6 5; CMe^, 25.4;
OAc, 24.3 (by direct titration). requires C, 53.3; n, 6.7; 2CKe^, 23.2; 20Ac, 23'
6.1.7* Oxidation of di-Q-isoPropylidene u-Gluoosone Hydrate by Periodate at Room Temperature.
a) Reduction of periodate. Pi-Q-aoetyl-di-O-isopropylidene O-glucosone hydrate (0.134g.) was dissolved in O.lN-sodium
hydroxide (12ml.) at 100®. The solution was cooled and neutr alised (inenolphthalein) by addition of O.lN-hydroohloric aoid. 0.265M-aodium periodate (2ml.) was added and the volume adjusted to 20ml. Jne periodate was determined on samples by the usual iodine-arsenite method; O.9 2 mole of periodate was reduced per mole of sugar in 2 hours, and 0.93 mole in 6 hours.
b) Formic acid production. Titration of a 6-hour sample (lOml.) showed that no )oid had been formed.
c) Formaldehyde production. The technique employed was that described by 3ell (1943). When the solution of di-O-isoprop- ylidene o-^lucosone hydrate obtained as in a) was oxidised under
these conditions the product formed (32.2mg. in 2 hours, 34. in 24 hours* from 23.2mg. of the di-O-aoetyl compound) on
188..
addition of dimedone had m.p. 140-150°. After a single
reorystallisation from ethanol (1ml.) the formaldehyde deriv ative, m.p. 184-1:^5° alone and mixed with an authentic sample, was obtained. 0.79 Mole of formaldehyde was formed per mole of the sugar in 2 hours, and O.SO mole in 24 hours.
By addition of water to the ethanolic mother liquor a orystalline product, m.p. 158-159* after two recrystallisations from
30%
ethanol, was isolated. The expected carbohydrate product is
1:2-2;3-di-Q-isopropylidene 5~aldo-o-xylosone hydrate; it would appear that its dimedone derivative is insoluble in water. The carbohydrate nature of the orystalline derivative was demonstr ated by a positive result in Molisch's test, and, after hydrol ysis with mineral acid, positive results in Benedict's copper reduction test and in the arsenophosphotungstic acid test; acetone was found to be present in the hydrolysate.
6.1.8. Méthylation of Di-Q-isoPropylidene o—Glucosone Hydrate. a) Beacetylation. The diacetate (l.Og.) was dissolved in dry methanol (40ml.) and sodium (30mg.) in methanol (6ml.) added. The mixture was allowed to stand at room temperature for 12 hours, and then evaporated under reduced pressure to a volume of 10ml.
b) Méthylation. To the above solution dry methyl iodide (10ml.) was added and the mixture refluxed for 1 hour during which time sodium iodide separated out. Anhydrous calcium sulphate (l.Og.) and fresh silver oxide (5*0g.) were added and reflux continued
for a further 4 hours. The mixture was extracted with dry
acetone (150ml.) and the extract evaporated to a syrup which was subjected to three further méthylations. The product was dis tilled in a vacuum (90-110°/0.05mm.) to yield syrupy di-£-methyl di-O-isopropylidene o-glucosone hydrate (0.37g., 43%), +1.2®
(c, 3 .3 in methanvl) (Found; OMe, 19-5» requires
6.1.9. Hydrolysis of Di-0-**etliyl-Di-Q-isoPropylidene o-Qluooaone Hydrate.
A solution of the di-£-msthyl derivative (50rag*) in methanol was evaporated to a small volume (0.25ml.), water (1ml.) and oonoentrated hydroohlorio aoid (2 drops) added, and the mixture heated at 100° for 10 minutes. The hydrolysate was neutralised by addition of solid sodium acetate. ^-Bromophenylhydraziae hydrochloride (0.2g.) and sodium acetate (ü.2g.) were added and heating- continued for a further 10 minutes. On cooling an oil separated out and crystallised on scratching. On reorystall- isauion from aqueous ethanol the derivative showed m.p. 154°; Salmon & Powell (1959) give m.p. I56® for 5:6-dl-£-methyl D-glucose j^-broraophenylosazone.
6.1.10. Oxidation of 5:6~Di-0-Methyl o-Glucosone.
To N-sulphuric aoid (2ml.) in an open dish heated on the boiling water bath was added dropwise a solution of di-£-methyl-di-0-
-isopropylidene p-glucosone hydrate (15ümg.) in methanol (4.5ml.). After 15 minutes heating to remove methanol the yellow solution was transferred to a conical flask and cooled. 10% Sodium
metaperiodate (6ml.) was added and the mixture set aside at room temperature for 72 hours. From the reaction product, by the method of Salmon & Powell (1959)» there was obtained a solution of u#-dimethoxypropionic aoid, identified as its j^-bromophen c/1 derivative (150mg., 64*5%).
(N.B. Alternative methods of preparation of tri-Q-isopropylidene o-gluocsone hydrate are outlined in Part II, 3.2.2.1.).
6.2. t-Glucosone.
6.2.1. iri-O-isoPropylidene l-Glucosone Hydrate.
When L-glucosone (l.Og.) was treated with acetone as described in 6.1.1., crystalline tri-O-isopropylidene t-gluoosone hydrate
(0.2g., 1 1.5%) was obtained, m.p. 125®, +6.8® (c, 2 .0 0 in methanol) (Found: C, 57.1$ H, 7.6%).