Enofuranose

Figure 1. Part of NMR spectrum of 5-deoxy-l, 2-O-iso-propylidene-3-O-tosyl-p-L-threo-pent-4-enofuranose (32) at 60 Mc.p.s. in deuterochloroform.

Of the four possible 5-deoxy-pent-4-enofuranoses, the D-erythro-isomer was of interest as a potential source of derivatives of L-lyxofuranose. For this purpose, a vinyl ether having the D-en/ hro-configuration has been prepared from derivatives of D-ribose. Condensation of D-ribose with acetone in the presence of methanol, cupric sulfate and sulfuric acid at 30°C., as described by Levene and Stiller(30) afforded a sirupy product consisting mainly of methyl 2,3-O-isopropylidene-D-ribofuranose (40). Treatment of a pyridine solution of the sirup with tosyl chloride... 

F rom 5-deoxy-5-iodo-1,2-0-isopropylidene-/ -l-arabinofura-nose (37). Anhydrous silver fluoride (600 mg.) was added to a solution of 300 mg. of 37 in pyridine (4.0 ml.), and the mixture was shaken at room temperature for 24 hours. Ether (4 ml.) was added, and the mixture was passed through a column of silica gel (1.5 X 12 cm.). The column was washed with ether/pyridine, 1 1 v/v. (10 ml.), and the effluent, which contained 5-deoxy-l,2-0-isopropylidene-/ -L-threo-pent-4-enofuranose (33), was concentrated to 4 ml. Acetic anhydride (0.2 ml.) was added, and the reaction mixture was kept at room temperature for 16 hours. Concentration afforded a sirup from which the last traces of solvent were removed by storage in high vacuum at 20°C. The sirup was distilled at 90°C. (bath) at 2.5 X HHmm. The distillate (110 mg., 51%), which crystallized on standing, had physical constants which were identical to material prepared as above. 

Deoxy-l,2-0-isopropylidene-3-0-tosyl-fi-i,- hxeo-pent-4-enofuranose (32). (1) From 5-deoxy-1,2-0-isopropylidene-/ -l-threo-pent-4-eno-... 

Deoxy-2,3-0-isopropylidene-f3-D-threo-hexulo-5-enofuranose (49). A solution of 860 mg. (2.5 mmole) of 48 in dry methanol (10 ml.) was treated with a solution of sodium methoxide (0.05 mmole) in methanol. The reaction mixture was stored at room temperature for 16 hours and then evaporated to dryness. The solid residue was dissolved in acetone, the solution filtered, and the filtrate evaporated to a small volume. Petroleum was added until the solution was faintly turbid the solution was then cooled. The resulting crystals (400 mg., 80%) were further purified by sublimation at 115°C. and 0.1 mm. m.p. 118°-120°C., [ ]D24 + 91.0° (c, 2.0). Anal Calcd. for C9H1405 C, 53.5 H, 7.0. Found C, 53.2 H, 6.9. 

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.

Deoxy-2,3-0-isopropylidene-/ -D-fhreo-hexulo-5-enofuranose 130, 6-Deoxy-2,3-0-isopropylidene-/ -D-arabino-hexuto furanose. . 131, 6-Deoxy kanamycin. ... 

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)... 

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

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... 

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