A-D-ribopyranose

T. Yoshida, C. Wu, L. X. Song, T. Uryu, Y. Kaneko, T. Mimura, H. Nakashima, and N. Yamamoto, Synthesis of cellulose-type polyriboses and their branched sulfates with anti-AIDS virus activity by selective ring-opening copolymerization of 1,4-anhydro-a-D-ribopyranose derivatives, Macromolecules, 27 (1994) 4422-4428. 

The division of the total computer-memory into sections allows the contents of one section to be added to or subtracted from those of another. This technique may sometimes be used to obtain the spectrum of one component of a mixture by subtraction of the spectrum due to other components from that of the mixture. For example, a 100-MHz spectrum of a-D-ribopyranose tetrabenzoate (1) has been... 

A small amount of each anomer was successfully obtained as crystals for mutarotation studies. The mutarotation curves are normal and, from this result, it was concluded that no significant proportions of the furanoses or of the aldehydo form appear during the mutarotation. This result contrasts with the complex mutarotation exhibited by )8-D-ribopyranose." The mutarotation of 5-thio-a-D-ribopyranose is strongly dependent on pH it shows a period of half-change of 10 hours at pH —4.4, and —7 minutes at pH —6.6. 

The condensation of acetone with D-ribose, with sulfuric acid as the catalyst, has also been examined in detail.17 The major component is 2,3-O-isopropylidene-D-ribofuranose (59%), together with three minor components l,5-anhydro-2,3-0-isopropylidene-D-ribofuranose (9%), 1,2 3,4-di-O-isopropylidene-a-D-ribopyranose (3%), and 1,2-0-isopropylidene-a-D-ribofuranose (6%). The authors observed that the only marked difference when other catalysts (such as copper sulfate or zinc chloride) were used was the absence of the anhydro compounds. Assuming that the 1-hydroxyl group is equatorial, the preponderance of the 2,3-acetal is consistent with the thermodynamic stability of the isomer having the least number of endo substituents and with the unfavorable interactions between the acetal rings in the 1,2 3,4-diacetal, which possesses a cis-syn-cis arrangement of rings.10... 

To facilitate the n.m.r. studies of the series of D-ribopyranose derivatives, use was made of a facility for the electronic subtraction of spectra. The spectrum of a-D-ribopyranose tetrabenzoate, which is not known in the pure form, was obtained at 100 Me./sec. by electronic subtraction of the spectrum of /3-D-ribopyranose tetrabenzoate from the mixture of anomers using the Varian C-1024 computer. 

An example of a sugar derivative held rigidly in a skew conformation is 3-0-benzoyl-l,2,4-0-benzylidene-a-D-ribopyranose (10). 

Isopropylidene 1,5-Anhydro-5 -bromo-2,3-O-isopropylidene-P-D-ribofuranose. 1,4-Anhydro-5S-bromo-2,3-0-isopropyli-dene-a-D-ribopyranose [93206-31-6]... 

Cryst. (dioxan/diisopropyl ether). Mp 109-110°. Mg -78.8 (c, 0.83 in H2O). Di-Ac 2,3-Di-0-acetyl-l,5-anhydro-P-D-ribofuranose. 2,3-Di-O-acetyl-l,4-anhy-dro-a-D-ribopyranose [51246-96-9]... 

Dibenzoyl 1,5-Anhydro-2,3-di-0-benzoyl-p-D-ribofuranose. l,4-Anhydro-2,3-dM-benzoyl-a-D-ribopyranose [111269-83-1]... 

Isopropylidene 1,5-Anhydro-2,3-0-isopro-pylidene-P-D-ribofnranose. 1,4-Anhydro-2,3-O-isopropylidene-a-D-ribopyranose [51246-99-2]... 

O-Isopropylidene 3,4-Dichloro-3,4-dideoxy-1,2-O-isopropylidene-a-D-ribopyranose C8H12CI2O3 227.086 Needles (CHCypetrol). Mp 171°. 

O-Isopropylidene See 1,2-0-Isopro-pylideneribose, 1-73 1,2-O-Isopropyli-dene-a-D-ribopyranose l,2 3,4-Di-0-isopropylidene l,2 3,4-Di-0-isopropyliderte-a-D-ribopyranose OiiHigO, 230.26 Mp 68-69°. [a]o -51 (CHCI3). 

Dichloro-3,4-dideoxy-l,2-0-isopropylidene-a-D-ribopyranose, D-545 6,6 -Dichloro-6,6 -dideoxymaltose, D-544... 

O -Isopropylidene-a-D-x y/o -pentodialdo-1,4-furanose, P-36 0-Isopropylidene-a-D-er yzAro-pentofuranos-3-ulose oxime, P-43 O -Isopropylidene-p-D-zAreo -pentulofuranose, P-48 O -Isopropylidene-5-0 -pivaloyl-a-D-glucofuranurono-6,3-lactone, G-539 0-Isopropylidenequinide, Q-10 O -Isopropylidene-L-rhamnitol, R-7 O -Isopropylidene-L-rhamnitol, R-7 0-Isopropylidenerhamnose, 1-72 O -Isopropylidene-D-ribono-1,4-lactone, R-128 O -Isopropylidene-a-D-ribopyranose, R-138 0-Isopropylidene-p-D-ribopyranose, R-138 0-Isopropylidene-D-ribose diethyl dithioacetal, R-140 0-Isopropylidene-D-ribose diethyl dithioacetal, R-140 0-Isopropylidene-D-ribose diethyl dithioacetal, R-140 0-Isopropylideneribose, 1-73 0-Isopropylideneribose, 1-74... 

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