Gulopyranoside

A mixture of d- and l- hexoses also results from the hydroboration of these 5-enes. Hydroboration results in anti-Markownikoff, cw-hydration of the double bond and the amount of each hexose formed varies according to the nature of the substituent groups. For example, hydroboration (23) of methyl 6-deoxy-a-D-ryZo-hex-5-enopyranose (3) affords methyl a-D-glucopyranoside and methyl / -L-idopyranoside in the ratio of 1 2.5 respectively whereas hydroboration of the fris-trimethylsilyl ether of 3 afforded them in the ratio 1 0.6 respectively. The hydroboration method can be used to achieve specific labelling of hexoses with tritium methyl-/ -L-idopyranoside[5-H3] and methyl a-D-glucopyranoside [5-H3] were thus prepared (23). Similarly, hydroboration of the D-Zt/ro-hex-5-eno derivative (14) with diborane-H3 followed by removal of the isopropyli-dene group, afforded methyl a-D-mannopyranoside [5-H3] and methyl / -L-gulopyranoside [5-H3] in the ratio of 1 2 respectively (23). 

Treatment of benzyl 2-acetamido-3,4-anhydro-2-deoxy-6-C>-trityl-a-D-allopyranoside (412) with tetrabutylammonium fluoride [BU4NF in refluxing (refl.) MeCN, 24 h] gave, under diaxial ring-opening, benzyl 2-acetamido-2,4-dideoxy-4-fluoro-6-f9-trityl-a -D-gulopyranoside (413), in... 

Phenyl 0-D-mannopyranoaide Methyl /S-n-gulopyranoside Phenyl S-D-galactopyranoside ... 

Benzyl 2-acetamido-3-0-acetyl-2,4-dideoxy-4-fluoro-6-0-trityl- a-D-gulopyranoside ... 

Benzyl-2-amino-2-desoxy-p-D-gulopyranosid-uronsaure-2,3-carbamat ) 80 4 62, 120)... 

Methyl 6-deoxy- 2,3-0-isopropylidene-a-D-gulopyranoside (lOg) Methyl 6-deoxy-2,3-0-isopropylidene-a-D-n7)o-hexopyranosid-4-ulose G [333]... 

With sodium hydroxide, methyl 2,3-anhydro-a-D-allopyranoside yields methyl 3,6-anhydro-a-D-glucopyranoside by intramolecular attack on the epoxide ring by the 6-hydroxyl group.72 Methyl 2,3-anhydro-a-D-gulopyranoside behaves similarly, and its intermediacy accounts for the conversion of methyl 3,4-anhydro-a-D-galactopyrano-side into methyl 3,6-anhydro-a-D-galactopyranoside on treatment with alkali.67... 

Neighboring-group participation by the vicinal, trans-acetoxyl group (see p. 125) serves to explain the abnormal behavior of methyl 4-0-acetyl-2,3-anhydro-6-0-benzyl- or -trityl-a-D-gulopyranoside with hydrogen chloride in acetone, or with 80% aqueous acetic acid, which give D-galactose, instead of the D-idose, derivatives.67 In the same way, 2-0-acetyl-3,4-anhydro-D-altropyranosides yield D-man-nosides, not D-idosides.9 6z(see p. 125). 

The third adduct (669) was an ether after similar functionalization of the dihydropyran ring to the L-gulo system, 3-0-(benzyl 4-deoxy-/3-L-gulopyranosid-4-yl)- l,2 5,6-di-0- isopropylidene-a-D- glucofuranose (672) was obtained. Cleavage of the ether bond between the sugar units was possible35 by alkaline -elimination. 

A similar orientation was found for the bromination of methyl 3,4-0-benzylidene-6-deoxy-/3-D-fucopyranoside (101), which gave135 methyl 4-0-benzoyl-3-bromo-3,6-dideoxy-D-gulopyranoside (102). It appears... 

C31H31BrN2O10 3-(4-Bromobenzamido)-4-hydroxy-8-methyl-7-[3-0-(5-methyl-2-pyrrolylcarbonyl)noviopyranosyloxy]coumarin71 P212l2I Z = 4 Dx = 1.448 R = 0.047 for 1,568 intensities. This compound is a 6-deoxy-6-methy 1-a-D-gulopyranoside, related to the antibiotics coumermycin A and novobiocin. The pyranosyl residue is in... 

J. L. Frahn, Preparation of the 2,3-anhydro-4,6-0-benzylidene derivatives of methyl a- and /J-D-talopyranoside and of methyl a-D-gulopyranoside, Aust. J. Chem., 33 (1980) 1021-1024. 

O. Mitsunobu, T. Kudo, M. Nishida, and N. Tsuda, Stereospecific and stereoselective reactions. 4. A one-step preparation of 2,3-anhydro-4,6-0-bcnzylidcnc- -i)-allopyrano-side and -gulopyranoside, Chem. Lett., (1980) 1613-1614. 

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