Galactal, 2-hydroxy

Subsequently this route to 3-deoxy sugars was developed by further work in our laboratory by Ferrier and Sankey (23). They demonstrated that although tetra-O-acetyl-2-hydroxy-D-galactal undergoes rearrangement in boiling acetic acid, and that reaction is speeded up and goes to completion if catalytic amounts of methanesulfonic acid are added, the... 

From the rearrangement of tetra-O-acetyl-2-hydroxy-D-galactal in boiling acetic acid it was possible to isolate l,2,4,6-tetra-0-acetyl-2,3-dide-h.ydro-3-deoxy-a-jy-threo-hexose (32) (58%) and a small amount of 1,2,3,4,6-penta-O-acetyl-jS-D-galactopyranose. In the reaction mixture the presence of some a-pentaacetate was demonstrated chromatographically but NMR spectroscopy indicated no resonances corresponding to the / anomer of compound 32. These spectral measurements indicate that compound 32 constituted 80% of the mixture of products. 

Today you can purchase D-galactal 5, D-glucal 10 and D- or L-fucal 20 e. g. peracetylated or with unprotected hydroxy groups. 

On the basis of the above directions but with variations in amounts, solvents, length of reaction time, and method of recovery, the following other substances have been made 2,3,4,6-tetra-0-acetyl-(2-hydroxy-D-galactal),2 9 yield 10% 2,3,4,6-tetra-0-benzoyl-(2-hydroxy-D-glucal),10 yield 65% 2,3,4-tri-0-acetyl-(2-hydroxy-D-xylal),n yield 28% 2,3,4-tri-0-benzoyl-(2-hydroxy-D-xylal),12 yield 11% 2,3,4-tri-0-benzoyl-(2-hy-droxy-L-xylal)12 2,3,4,2,3,4,6 -hepta-0-acetyl-(2-hydroxygentiobial),18 yield 50% 2,3,6,2,3, 4,6 -hepta-0-acetyl-(2-hydroxycellobial),9 yield 58% and 2,3,6,2, 3,4, 6/-hepta-0-acetyl-(2-hydroxylactal),8 yield 44%. Major and Cook12 reported their failure to obtain a crystalline tri-O-acetyl-(2-hydroxyxylal). Fletcher and Hudson crystallized the D-isomer from acetic acid by the addition of water. 

The position of the double bond in the 2-hydroxyglycals has been verified in two instances by isolation of the five-carbon fragment resulting on oxidation with potassium permanganate in the presence of potassium carbonate. From 2,3,4,6-tetra-0-acetyl-(2-hydroxy-D-glucal) there was recovered potassium tri-O-acetyl-D-arabonate in 87.8% yield. Its identity was confirmed by conversion to the phenylhydrazide after deacetylation.1 Similarly, 2,3,4,6-tetra-0-acetyl-(2-hydroxy-D-galactal) was converted to potassium D-lyxonate, the identity of which was confirmed by conversion to the lactone.9... 

Osone hydrates have been prepared from 2,3,4,6-tetra-0-acetyl-(2-hydroxy-D-glucal)1 and from the corresponding derivatives of 2-hydroxy-D-galactal,9 2-hydroxyceIlobial13 and 2-hydroxygentiobial.13 Hydrolysis of the dichloride may be effected simply by the addition of a little water to its solution in ether or benzene, but more often silver carbonate or sodium bicarbonate is added to neutralize the hydrogen chloride produced. Sodium and potassium carbonate are too alkaline and result in yellowing of the reaction mixture. A yield of 90% of the theoretical amount of osone hydrate was obtained from the crystalline dichloride derived from D-glu-cose. However, the crystalline dichloride derived from cellobiose resisted hydrolysis (see the previous Section). Nevertheless, the cellobiosone hydrate was prepared from the sirupy mother liquor. In any case, yields on the basis of the entire, chlorinated substances were low.1613... 

An amorphous preparation was made similarly from 2,3,4,6-tetra-O-acetyl-(2-hydroxy-D-galactal).9 It was noted that this preparation did not give the reactions reported by Helferich for the 5,6-anhydro derivative with pyrogallol, orcinol, aniline, and m-nitroaniline. However, it did give a voluminous, red-brown precipitate with phloroglucinol. 

Phenylosazone of monoacetate from 2,3,4,6-tetra-O-acetyl-(2-hydroxy-D-glucal) or -d-galactal... 

The C22-C27 segment 149 was prepared from tri-O-acetyl-D-galactal (151) ( Scheme 16). Treatment of 151 with methanol in the presence of SnCl4 afforded 152 (Ferrier-t) e 0-glyco-sidation). Deacetylation of 152 followed by monosilylation provided 153. Hydroxy-direct-... 

Yields of the products vary considerably, and are influenced by a competing elimination reaction. From D-glucal and D-galactal, for example, in addition to the 2-deoxyhexoses (42% and 78%, respectively), 3-hydroxy-2-(hydroxymethyl)-2-pyran (12) was isolated in 16% and 1% yield,... 

The unusual structure of l-(9-adenyl)-6-deoxy-2-hydroxy-L-galactal (72) has been assigned to a compound related to the antibiotic substance psicofuranine, and the evidence on which the assignment was based has been summarized in this Series. ... 

Acetamido-2-deoxy-a-D-talopyranosides of serine and two hexose derivatives, e.g. 23, were synthesized from tetra-O-benzoyl-2-hydroxy-D-galactal 21 via... 

A related rearrangement of the enolone (13) gave the unsaturated C-glycoslde derivative (l4) in yield (Scheme 7), and prolonged treatment of tetra-O-acetyl-2-hydroxy-D-glucal or -galactal with... 

Scheme 18.23 Oxidant for pseudothioglycal oxidation varies with protecting groups (Danishefslw. 1991 Rojas. 2001 and application of Mislow-Evans rearrangement with a galactal-derived 4-hydroxy-6-deoxy derivative.—...

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