Arabinose derivs

The asymmetric synthesis of / -branched carboxylic acid derivatives was accomplished by conjugate addition of mixed organoaluminum reagents to optically active Arabinose-derived c -unsaturated A-acyloxazolidinones (Scheme 47). Efficient stereocontrol was achieved using different optically active bicyclic oxazolidinones, yielding (.R)- or ( -configured / -branched carboxylic acid derivatives.136a... 

On oxidation of the phenylosotriazole derivative of the disaccharide with sodium periodate, three moles of periodate are consumed with the formation of one mole each of formic acid and formaldehyde per mole of the phenylosotriazole derivative. If the D-glucose in the u-glucopyrano-syl-L-arabinose phenylosotriazole were attached to carbon atom 4 of the L-arabinose derivative, oxidation of this compound with sodium periodate would require two moles of periodate and would liberate one mole of... 

Fig. 4 Comparison of the relevant stereogenic centers in the d-arabinose derivative 121 and in preussin (2)...

Shing and coworkers reported arabinose-derived uloses (59, 60) as epoxidation catalysts, and phenyl stilbene can be epoxidized by 60 in up to 90% ee (Fig. 20) [113-115]. In 2003, Zhao and coworkers reported aldehyde 61 to epoxidize trans-stilbene in up to 94% ee [116]. 

An efficient stereoselective synthesis of the (pyrrolidin-2-ylidene)glycinate intermediate 325 was reported in a total synthesis of carzinophilin (326), employing an intramolecular cycloaddition of an azide with an alkene (63) (Scheme 9.63). The arabinose derivative 319 was converted into the required azide 321 via the triflate 320. Thermolysis of the azide 321 at 50 °C in THF produced the unstable triazoline 322, which on rearrangement gave the (pyrrolidin-2-ylidene)glycinate 325 in 60-72% overall yield from the triflate 320. 

The enantiomorph, also a syrup, was synthesized from 3,6-anhydro-4,5-O-isopropylidene-D-mannitol18 by periodate oxidation to the corresponding D-arabinose derivative, followed by reduction in the presence of Raney nickel.17 2,5-Anhydro-D-xylitol, 2,5-anhydro-D-ribitol, and 2,5-anhydro-D-lyxitol (1,4-anhydro-D-arabinitol)19,20 were... 

CATALYTIC ENANTIOSELECTIVE EPOXIDATION OF TRANS-DISUBSTITUTED AND TRISUBSTITUTED ALKENES WITH ARABINOSE-DERIVED ULOSE... 

We recently reported our results on the asymmetric epoxidation of trans-disubstituted and trisubstituted alkenes, using Oxone as oxidant, catalyzed by readily available arabinose-derived 4-uloses containing tunable steric blockers that control the enantioselectivity of the epoxidation.Ulose (3), containing a 2, 3 -diisobutyl acetal unit, was the most efficient catalyst and displayed good enantioselectivity. 

Examples of these convenient chiral building blocks reviewed in this chapter include levoglucosenone, isolevoglucosenone and L-arabinose derivatives. 

To a mixture of glucopyranose (0.22 mmol) in dry cyclohexane (24 ml) under an argon atmosphere were added iodosylbenzene (0.43 mmol) and iodine (0.22 mmol) at room temperature. The mixture was stirred for 20 h at the same temperature. After the reaction, the reaction mixture was poured into water and extracted with ether. The organic layer was washed with aq. sodium thiosulfate solution, water, and dried over Na2S04. After removal of the solvent, the residue was chromatographed on silica gel (eluent hexane/ethyl acetate = 65/35) to give D-arabinose derivative in 86% yield [68]. 

During the same study, the Italian researchers aiming at the synthesis of carbaoctanose compounds (vide infra), synthesized a nine-carbon long intermediate 308 which served both to access the octanose and the septanose targets. As shown in Scheme 50, the route to 308 entailed vinylogous aldol coupling between pyrrole 76 and D-arabinose derived aldehyde 306 producing lactam 307, the immediate precursor of 308. To... 

From a study of several compounds, it appears that a 2-hydroxyl trans to the phosphate strongly favours the formation of the phospholipid anion. The ribose derivative differs from the arabinose derivative only by the trans configuration of the 2-hydroxy group with respect to the phosphate. 

In the same year, Wolfrom and Foster synthesized certain 2-0-[(alkyl-thio)thiocarbonyl] derivatives of methyl 3,4-0-isopropylidene-iS-D(and l)-arabinopyranoside and of methyl 4,6-0-benzylidene-3-0-methyl- -D-altro-pyranoside by the action of carbon disulfide on the appropriate 2-0-sodio compounds, followed by treatment with an alkyl halide. The halides used— methyl iodide and triphenylmethyl iodide—were chosen for their ability to cause (S-alkylation rather than transformation to a thionocarbonate (see p. 110). The D- and L-arabinose derivatives could be converted to 2-deoxy-o-eri/ /iro-pentose (see p. 141). 

D-Arabinose derivatives Bis(metby] 3,4-0-i opropylidene- 8 D-arabinopyranoside) 2,2 -tbionooar-bonate 210-211 -254 C H, J, K 31... 

Scheme 13 Synthesis of a polymer-bound arabinose derivative by Zard [10]...

Nucleosides such as (246) have been prepared by the coupling of the trimethylsilyl derivative of (244) with 2,3,5-tri-0-acetyl-j8-D-ribofuranosyl bromide (245) followed by deacetylation (75JOC3708). Arabinose derivatives substituted at N-1 have also been prepared (76JMC814). 

Horton et al. were interested in the synthesis of tetra-C-substituted carbocycles, and extensively studied asymmetric Diels-Alder reactions employing acyclic unsaturated carbohydrate derivatives. Thus, the thermal cycloaddition of the D-arabinose-derived c/i-dienophile (Z)-100 with cyclopentadiene gave endo-adduct 101 in excellent optical purity. The high diastereo-facial differentiation in this reaction arises from a highly favored conformation at the allylic center [76,77] (Scheme 10.33). Therefore, conformer 102 seems to be more favored than 103, where the latter suffers from severe allylic strain between the methoxycarbonyl and the C4-acetoxy group... 

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