Mannopyranoside methyl 4,6-0-ethylidene

The stereoselective introduction of an ethynyl group in various flve- and six-membered iodohydrins has also been developed by the same group (O Scheme 37) [60]. Treatment of 3 -ethynyldimethylsilyl 2-deoxy-2-iodo-D-mannopyranoside 142 with Et3B and TBAF in toluene furnished the methyl 2-deoxy-2-C-ethynyl-4,6-0-benzylidene-a-D-mannopyranoside 144 in 85% yield. However, a similar reaction of 3-iodo-D-ribosyl substrate 143 having the [2-(trimethylsilyl) ethynyl]dimethylsilyl at C-5 gave the desired product 5-0-acetyl-3-deoxy-3-C-ethynyl-l,2-0-(l-methyl ethylidene)-a -D-xylofuranose, in which the ethynyl group was introduced at the y-cis position to the 5 -hydroxyl, in only 31% yield. This may be explained by an unfavored 6-exo radical cyclization. 

Quantum yields were determined, and the mechanism was discussed as a function of the temperature of the reaction, the structure of the substrate, and the effect of the dissolved oxygen. The formation of the 4- and 6-O-benzoyl derivatives 65 and 66 was later confirmed,87 and preliminary experiments conducted on methyl 2,3 4,6-di-0-ben-zylidene-a-D-mannopyranoside and on methyl 2,3-di-O-benzoyl-4,6-O-benzylidene-a-D-gluco- and -galacto-pyranosides were reported.88 Further results in the field were obtained for an O-ethylidene deriva-... 

If the reaction takes place via an anion or in a S 2 fashion, high yields of the product alkyl-cyclopropanes have been obtained. Thus, reaction of methyl 4,6-( -benzyIidene-2,3-dideoxy-2,3-C-[(7 )-(chloromethyl)ethylidene]-a-D-mannopyranoside (1) with lithium aluminum hydride in refluxing tetrahydrofuran gave methyl 4,6-0-benzylidene-2,3-dideoxy-2,3-C-isopropylidene-a-D-mannopyranoside (2) in 89% yield. Similarly, treatment of chloromethylcyclopropane 3 with lithium triethylborohydride, followed by oxidation with pyridinium chlorochromate,. gave ishwarone (4) in 75% yield. ... 

Methyl 4,6-benzylidene-2,3-dideoxy-2,3-C-[(/t)-(chloromethyl)ethylidene]-a-D-mannopyranoside (1.90 g, 5.86 mmol) was dissolved in dry THF (300 mL), an excess of LiAlH4 (250 mg, 6.58 mmol) was added, and the mixture was refluxed. After 12 h, TLC indicated that the reaction was complete and a new compound had formed [/tyO.53, aluminum sheets precoated with silica gel 60 (HF 254) to a thickness of 0.2 mm, EtOAc/petroleum ether bp 30-60 °C 1 4]. The mixture was cooled to rt, EtOAc was added to destroy the excess L1AIH4, and the resulting suspension was filtered through Celite and evaporated to dryness. The residue was chromatographed (silica gel, EtOAc/petroleum ether bp 30-60°C 1 4) yield 1.51 g (89%) clear syrup. 

With paraldehyde and sulfuric acid at room temperature, methyl 4,6-0-ethylidene-a-D-mannopju anoside (32%) and methyl 2,3 4,6-di-0-ethyli-dene-a-D-mannopyranoside (55%) were isolated. The corresponding (8-d anomers have also been prepared. Assuming that the CA conformation is the most probable, the 4,6-acetals of methyl mannopyranosides are readily available model compounds for comparing the reactivities of equatorial (C-3) and axial (C-2) hydroxyl groups in the pyranoid ring. 

Tosyl Methyl 4,6-0-ethylidene-2-0-tosyl-a-D-mannopyranoside C16H22O8S 374.411... 

Methyl 2,3-dideoxy-5- O -trityl-a-D-g/ycero -pent-2-enofuranoside, D-650 Methyl 2,3-dideoxy-5-0-trityl-p-D-g/ycero -pent-2-enofuranoside, D-650 Methyl 2,3 4,6-di-0-ethylidene-a-D-dlopyranoside, M-148 Methyl 2,3 4,6-di-0-ethylidene-a-D-mannopyranoside, M-180 Methyl 2,3 4,6-di-0-ethylidene-p-D-mannopyranoside, M-180 Methyl a-D-digitoxoside, D-612 Methyl a-L-digitoxoside, D-612 Methyl a-dihydrostreptoside, D-230 Methyl p-dihydrostreptoside, D-230... 

Methyl 5-ethenyl-2,2-dimethyl-l,3-dioxolane-4-carboxylate, D-708 Methyl (ethyl 2,3,4-tri-0-benzyl-l-thio-p-D-glucopyranosid)uronate, T-75 Methyl 3,4-0-ethylidene-p-L-arabinopyranoside, M-153 Methyl 4,6-0-ethylidene-2,3-di-0-metiiyl-p-D-galactopyranoside, M-186 Methyl 4,6-0-ethylidene-2,3-di-0-methyl-a-D-niannopyranoside, M-180 Methyl 4,6-0-ethylidene-2,3-di-0-tosyl-a-D-glucopyranoside, M-190 Methyl 4,6-0-ethylidene-2,3-di-0-tosyl-a-D-mannopyranoside, M-180 Methyl 4,6-O-ethylidene-a-D-galactopyranoside, M-185 Methyl 3,4-O-ethylidene-p-D-galactopyranoside, M-186 Methyl 4,6-O-ethylidene-a-D-glucopyranoside, M-190 Methyl 4,6-0-ethylidenemannopyranoside, M-180 Methyl 4,6-0-ethylidene-2-0-methyl-a-D-altropyranoside, M-149 Methyl 4,6- O -ethylidene-2-0 -methyl-a-D-arafeiwo -hexopyranosid-3-ulose, H-95... 

Methyl 6-0-acetyl-2,3-di-O-benzyl-a-D-mannopyranoside, M-204 Methyl 4-0-acetyl-2,3-di-0-methyl-a-D-mannopyranoside, D-748 Methyl 4-0-acetyl-2,3-0-isopropylidene-6-0-methyl-a-D-mannopyranoside, M-200 Methyl 4-O-acetyl-a-D-mannopyranoside, M-204 Methyl 6-O-acetyl-p-D-mannopyranoside, M-205 Methyl 4-0-acetyl-6-0-methyl-a-D-mannopyranoside, M-274 Methyl 2-0-acetyl-3,4,6-tri-0-benzyl-a-D-mannopyranoside, M-204 Methyl 4-0-acetyl-2,3,6-tri-0-methyl-a-D-mannopyranoside, T-190 Methyl 3-amino-3-deoxy-p-D-mannopyranoside, A-313 Methyl 3-amino-3-deoxy-a-D-mannopyranoside, A-313 Methyl 2,3-anhydro-4,6-0-benzylidene-(3-D-mannopyranoside, M-169 Methyl 2,3-anhydro-4,6-0-benzylidene-a-D-mannopyranoside, A-676 Methyl 2,3-anhydro-4-0-benzyl-6-0-trityl-a-D-mannopyranoside, A-676 Methyl 2,3-anhydro-4,6-di-0-methyl-p-D-mannopyranoside, A-676 Methyl 2,3-anhydro-4,6-di-0-tosyl-a-D-mannopyranoside, A-676 Methyl 2,3-anhydro-4,6-0-ethylidene- -D-mannopyranoside, A-676 Methyl 2,6-anhydro-a-D-mannofuranoside, A-671 Methyl 3,6-anhydro-a-D-mannofuranoside, A-679 Methyl 2,3-anhydro-a-D-mannopyranoside, 8CI, A-676 Methyl 2,3-anhydro-p-D-mannopyranoside, A-676 Methyl 2,6-anhydro-a-D-mannopyranoside, A-678 Methyl 3,6-anhydro-a-D-mannopyranoside, A-679 Methyl 3,6-anhydro-p-D-mannopyranoside, A-679 Methyl 2,3-anhydro-6-0-trityl-a-D-mannopyranoside, A-676 Methyl 6-azido-6-deoxy-2,3-0 -isopropylidene-a-D-mannofuranoside, A-913... 

Methyl 2,3-diacetainido-2,3-dideoxy-a-D-mannopyranoside, D-449 Methyl 2,3-diacetamido-2,3-dideoxy-p-D-mannopyranoside, D-449 Methyl 3,6-diacetamido-3,6-dideoxy-a-D-mannopyranoside, D-451 Methyl 3,4-di-0-acetyl-2,6-anhydro-a-D-niannopyranoside, A-67S Methyl 3,4-di-0-acetyl-2,6-anhydro-p-i>mannopyranoside, A-67S Methyl 2,3-di-0-acetyl-4,6-0-benzylidene-a-D-mannopyranoside, M-169 Methyl 2,4-di-0-acetyl-3,6-di-0-benzoyl-a-D-mannopyranoside, M-204 Methyl 4,6-di-0-acetyl-2,3-di-0-benzyl-a-D-mannopyranoside, M-204 Methyl 2,3-di-0-acetyl-4,6-0-ethylidene-a-D-mannopyranoside, M-I80 Methyl 5,6-di-0-acetyl-2,3-0-isopropylidene-a-D-mannofuranoside, 1-71 Methyl 4,6-di-O-acetyl-a-D-mannopyranoside, M-204 Methyl 2,3-di-0-acetyl-4,6-0-methylene-a-D-mannopyranoside, M-204 Methyl 2,3-diamino-2,3-dideoxy-p-D-mannopyranoside, D-449 Methyl 3,6-diamino-3,6-dideoxy-a-D-mannopyranoside, D-451 Methyl 3,6-di-0-benzoyl-2,4-di-0-methyl-a-D-mannopyranoside, D-749 Methyl 3,6-di-O-benzoyl-a-D-mannopyranoside, M-204 Methyl 2,6-di-0-benzoyl-3-0-methyl-p-D-mannopyranoside, M-205 Methyl 2,3-di-0-benzyl-4,6-0-benzylidene-a-D-mannopyranoside, M-169 Methyl 2,3 4,6-di-0-benzylidenemannopyranoside 0L-i>-( R, R)-form, M-172... 

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