Hex-5-enofuranose

CnHl7N05 2-Acetamido-2,3-dideoxy-5,6-0-isopropylidene-a-D-en/thro- hex-2-enofuranose AMIHXF 37 385... 

P. Koll and D. Eisermann, 1,6-Anhydrofuranoses. 20. Synthesis of two 1,6 2,3-dianhydrohexofuranoses by Payne oxidation of l,6-anhydro-5-0-benzoyl-2,3-dideoxy-/l-D-eryt/jro-hex-2-enofuranose and 1,6-anhydro-5-0-benzoyl-2,3-dideoxy-a-L-tAreo-hex-2-enofuranose, J. Carbohydr. Chem., 7 (1988) 757-771. 

Studies have also been made of 3-deoxy-2,5,6-tri-0-methyl-D-en/thro-hex-2-enofuranose (42, R = H, R = Me), prepared from 2,3,5,6-tetra-O-methyl-D-glucofuranose.80 The derived methyl glycosides were separated, and were found to be very acid-labile, affording black polymers under several conditions, but, on reaction with methanol, they gave the methyl 3-deoxy-5,6-di-0-methyl-D-glycero-hex-3-eno-sidulose dimethyl acetals which, like the unsaturated free sugar, gave 5-(D-g/ycero-l,2-dimethoxyethyl)-3(2H)furanone (44) on hydrolysis. 

Similar /3-eliminations occur with 2-acylamino-2-deoxyaldoses, and an enamine derivative believed to be 2-acetamido-2,3-dideoxy-D-erj/after treatment of 2-acetamido-tetra-O-acetyl-2-deoxy-/3-D-glucose under basic conditions (91) was also thought to be the first product formed in the Morgan-Elson test for 2-acetamido-2-deoxyhexoses. < >> Although furan compounds are ultimately formed in this reaction, there would seem to be small reason to doubt that a single elimination from a simple derivative of n-glucose would give an unsaturated, pyranoid product. 

Brief oxidation with 0.025 M-sodium metaperiodate at pH 7, followed by estimation with the resorcinol or thiobarbituric acid reagent, has been used in the simultaneous assay of free and ketosidically bonded sialic acids, respectively." Treatment of 2-acetamido-2-deoxy-3,4 5,6-di-O-isopropylidene-aW liydo-D-glucose (192) or the analogous D-mannose derivative with alkali gave 2-acetamido-2,3-dideoxy-5,6-0-isopropylidene-a-D-eryt/iro-hex-2-enofuranose (193), which afforded the methyl 2-enofuranosides (194) with acidified methanol-acetone (194)... 

An aq. soln. of 3-deoxy-2-0-methyl-) -D-erp /iro-hex-2-enofuranose added gradually to aq. NaBH4, warmed to 40°, allowed to stand overnight, excess reagent destroyed with acetone, and the Na -ions removed with a sulfonated... 

All derivatives used were prepared by essentially standard literature procedures and had physical constants in accord with previously reported values. Furthermore, the P.M.R. spectra were in each case consistent with the assigned structures. All solutions were concentrated under reduced pressure and m.p. s are uncorrected. (I) 2-Deoxy-D-arafczno-hexopyranose was a commercial sample from Pfanstiehl Lab. Inc., Waukegan, Illinois and was used without further purification. (II) 3, 4, 6-Tri-O-acetyl-D-glucal (1) was a commercial sample from Aldrich Chem. Co., Milwaukee, Wisconsin and was purified by distillation and recrystallized three times from aqueous ethanol. (Ill) 1, 3, 4, 6-tetra-0-acetyl-2-deoxy-a-D-arahino-hexopyranose (4) was prepared by the method of Bonner (11) while the corresponding / -anomer (5) was synthesized following the procedure of Overend, Stacey, and Stanek (47). (IV) 5, 6-Dideoxy-1, 2-0-isopropylidene-a-D-xj/io-hex-5-enofuranose (20) was provided by A. Rosenthal and G. Khan of this Department. 

Figure 6. Partial 100 MHz P.M.R. Spectrum of 5,6-Dideoxy-l,2-0-isopro-pylidene-a-D-xy o-hex-5-enofuranose (20) in CHCl3 solution.

Anhydro-a-D-fructofuranose 3,6-anhydro-P-D-fructofuranose 1,2 2,l -dianhydride (64) 6-Azido-6-deoxy-a-D-fructofuranose 6-deoxy-P-D-t/ reo-hex-5-enofuranose 1,2 2,1 -dianhydride" (65) 6-5-Heptyl-6-thio-a-D-fructofuranose 6-deoxy-p-D-tft eo-hex-5-enofuranose 1,2 2,l -dianhydride" (66) 4,5 4, 5 -Di-0-isopropylidene-di-p-D-fructopyranose 1,2 2,l -dianhydride (67) 6,6 -Dideoxy-6,6 -diiodo-di-p-D-fructofuranose 1,2 2,1 -dianhydride (68)... 

Scheme 2.—Proposed Mechanism for Photochemically Initiated, Radical Addition of 1,3-Dioxolane to 5,6-Dideoxy-l,2-0-isopropylidene-a-D-xi//o-hex-5-enofuranose (3).

Treatment of 3-deoxy-l,2 5,6-di-0-isopropylidene-a-D-erythro-hex-3-enofuranose with iodine and thallous fluoride in anhydrous ether afforded227 3-deoxy-l-fluoro-3-iodo-l,2 5,6-di-0-isopropyli-dene-D-xy/o-4-hexulose in 80% yield, together with small proportions of (tentatively identified) 3-deoxy-4-fluoro-3-iodo-l,2 5,6-di-0-iso-propylidene-a-D-allofuranose and two unidentified products. A mechanism proposed for the furanose ring-opening involves the formation of a 3,4-iodonium ion, and attack by fluoride at C-l. 

Coupling constants (4/f,h) have been observed in a few instances where fluorine is attached to sp2-hybridized carbon, as, for example, in derivatives of 3-deoxy-3-C-(fluoromethylene)-l,2 5,6-di-O-isopropyli-dene-a-D-ribo- and -xylo-furanose, where JF, h-2 and 4/F, h-4 occur254,264 in the range of 0.5-5.5 Hz, and in 5,6-dideoxy-6,6-difluoro-l,2-0-isopropylidene-3-0-methyl-a-D-xylo-hex-5-enofuranose,251 where 4JFete, h-4 = 2.0 Hz and VFtran. h-4 = 1.5 Hz (cis and trans, relative to H-5). 

Values for 7f.c have been recorded251 for fluorine attached to sp2-hy-bridized carbon, as in 5,6-dideoxy-6,6-difluoro-l,2,0-isopropylidene-3-0-methyl-a-D-3cyio-hex-5-enofuranose, where lJftC = 285 Hz. The signs of the 7f,c values both for the pyranosyl and the furanosyl fluorides were found to be negative.278... 

The addition of the pseudohalogen iodine azide (prepared from iodine monochloride and sodium azide in acetonitrile) to methyl 5,6-dideoxy-2,3-di-0-p-tolylsulfonyl-a -L-arabtno-hex-5-enofuranoside has also been achieved a crystalline /3-iodo azide was isolated, in 69% yield, that was stable in the dark, but became colored on exposure to light.130 Brimacombe and coworkers133 have reported the addition of iodine azide to 5,6-dideoxy-l,2-0-isopropylidene-o -D-xy/o-hex-5-enofuranose X-ray crystallographic analysis established that the product is 6-azido-5,6-dideoxy-5-iodo-l,2-0-isopropylidene-/3-L-idofuranose. 

The addition of iodine trifluoroacetate (produced by reaction of iodine with silver trifluoroacetate) to unsaturated carbohydrates has been investigated.134 Treatment of 5,6-dideoxy-l,2-0-isopropylidene-a-D-xylo-hex-5-enofuranose (89) with silver trifluoroacetate and iodine in acetonitrile gave 3,6-anhydro-5-deoxy-5-iodo-l,2-0-iso-propylidene-a-D-gluco(and /3-L-ido)furanose (91) and 5-deoxy-5-iodo-l,2-0-isopropylidene-6-0-(trifluoroacetyl)-o -D-gluco(and/or /3-L-ido)-furanose (92), with the former preponderating. Component 91 was converted into 3,6-anhydro-5-deoxy-l,2-0-isopropylidene-a-D-xj/io-hexofuranose (94) by hydrogenation over Raney nickel (see also, Section III,3 p. 299), and component 92 was converted into 5-deoxy-l,2-0-isopropylidene-a-D-xy/o-hexofuranose (95) by treat-... 

Addition of dichloromethylene to 3-deoxy-l,2 5,6-di-0-isopropyli-dene-a-D-erythro-hex-3-enofuranose gives 3-deoxy-3,4-C-(dichloro-methylene)-l,2 5,6-di-0-isopropylidene-a-D-galactofuranose.51 [The... 

A similar situation is found in 6-azido-5,6-dideoxy-5-iodo-1,2-0-isopropylidene-/3-L-idofuranose, prepared by the action of iodine azide (IN3 a pseudohalogen) on 5,6-dideoxy-l,2-0-isopropylidene-a-D-xylo-hex-5-enofuranose.53 The addition of iodine azide to the... 

Potassium selenocyanate with 2 (or the c-ido isomer) yieldsss l,2-0-isopropylidene-a-D-xy(o-hex-5-enofuranose (65) by elimination of the oxirane oxygen atom. A similar elimination had earlier been... 

II) From Vinylic Ethers.—The base-catalyzed elimination of certain tosyloxy functions in carbohydrates was demonstrated as early as 1922 by Freudenberg and Brauns.118 From the reaction of 1,2 3,6-dHO-isopropyl-idene-3-O-p-tolylsulfonyl-D-glucofuranose (16) with anhydrous hydrazine, they obtained, in addition to the 3-hydrazino derivative, 3-deoxy-l, 2 5,6-di-0-isopropylidene-D-erj/(Aro-hex-3-enofuranose (17). Hydrogenation of... 

The use of the pseudohalogen nitryl iodide, prepared in situ from iodine and silver nitrite, has been found to add to an alkene in what is strictly an anti-Markownikov fashion. The explanation for this lies in that nitryl iodide adds in a radical manner, initially forming the more stable secondary radical after addition of NO2.115 Treatment of 3-0-acetyl-5,6-dideoxy-1,2-0-isopropylidene-a-D-xy/o-hex-5-enofuranose with nitryl iodide was found to afford an unstable adduct, with the nitro group appended to C-6, and iodine attached to the more substituted C-5.116-118 Similarly, treatment of benzyl 2-0-benzyl-3,4-dideoxy-a-D-g/ycero-pent-3-enopyranoside (70, Scheme 19) with nitryl iodide afforded the unstable adduct 71, which, upon exposure to mild base (NaHC03), afforded the eliminated product, namely benzyl 2-0-benzyl-3,4-dideoxy-4-nitro-a-D-g(ycew-pent-3-enopyranoside (72). The eliminated product was then readily converted into benzyl 2-0-benzyl-3,4-dideoxy-(3-L-r/ireo-pentopyranoside (73) by reduction with sodium borohydride. Addition of deuteride using NaBD4 led to axial deuteration atC-3. 

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