Arabino- Configuration

An interesting example from carbohydrate chemistry is the boron trifluoride-diethyl ether complex catalyzed nucleophilic addition of silyl enol ethers to chiral imines (from n-glyceralde-hyde or D-serinal)22. This reaction yields unsaturated y-butyrolactones with predominantly the D-arabino configuration (and almost complete Cram-type erythro selectivity). 

In order to simplify these preparations, Boivin et al. [52] made use of the allylic rearrangement reaction (Ferrier type) which was one of the first accesses to 3-amino glycals. By use of azide as the nucleophile, the L-arabino configurated glycal 78... 

The assignment of the configuration of the deoxyiodonucleoside as being arabino (CVIa) or ribo (CVIb) is surely warranted. The arabino configuration could arise by inversion at C2, with displacement of the tosylate ion of LXXXVI. The fact that the deoxyiodonucleoside (CVI), as well as LXXXVI (R = H), is converted to the anhydronucleoside LXXXVII by means of methanolic ammonia126 would be consonant with either configura-... 

Consider the ketose shown. It has three chiral carbon atoms in the D-arabino configuration (even though interrupted by a keto group). The keto group is at position 3. The ketose has six carbon atoms. It is therefore called D-araW o-3-hexulose. 

The simplest known sugar derivatives that interact with the jack-bean lectin are l,5-anhydro-2-deoxy-D-arahino-hexitol and 1,4-anhydro-D-arabinitol.168,215 These alditols contain the minimal structural features required for binding to con A, namely, unmodified hydroxyl groups of the B-arabino configuration at C-3, C-4, and C-5 of the... 

In extracts of a wild type of E. coli (Strain B), enolpyruvate phosphate and D-erythrose 4-phosphate are converted to a 3-deoxyheptulosonic acid (most probably of the arabino configuration) and two equivalents of orthophosphate. Since 3-deoxy-D-arai fno-heptulosonic acid 7-phosphate was readily dephosphorylated by these enzyme preparations, the conclusion was... 

The first synthesis of arabino-configured cyclic phosphonomethylphosphin-ates (397) has been accomplished. The crucial step of this synthesis consisted in the condensation of H-phosphinylphosphonate (398) with hydroxyaldehyde (399) derived from D-arabinol derivative followed by cyclization of (398) induced under acylation conditions (Scheme 98). 

If the two lowest asymmetric carbon atoms possess the D-erythro configuration, a -D-glucosaccharinic acid must be either 2-C-methyl-o-arabmo-pentonic acid or 2-C-methyl-D-ribo-pentonic acid. The initial choice between these two possibilities was made by Nef, who chose the D-arabino configuration because of similarities between certain alkaloid salts of the saccharinic acid and the corresponding salts of n-arabinonic acid. However, subsequent developments make the D-ribo configuration appear the more... 

The inability of these enzymes to cleave the furanosyl bond in the arabino analogs argues against catalysis by strain. There is no obvious reason why an arabino configuration should so effectively preclude the requisite distortions,... 

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