A Novel Deoxygenation of Hydroxy Groups Activated by a Vicinal Carbonyl Group via Reaction with Ph 3 P/I 2 /Imidazole 1 2 (original) (raw)
Formation of 1,5-lactones from 3-deoxy-d-manno-2-octulosonic acid derivatives
Tetrahedron Letters, 1987
Acylation of ammonium 3-deoxy-n-D-manno-Z-octulopyranosonate (la) leads to the formation of peracetylated 3-deoxy-a-D-manno-2-octulopyranosono-1,5-lactones (3a,b). The proposed structures were confirmed by independent syntheses. The 1,7-lactone was not formed even when only OH-7 was available for lactonisation.
Carbohydrate Research, 1995
The well-known /3-elimination of protected aldonolactones is used for the synthesis of the short-chain 2-keto-3-deoxyaldonic acids 1-4 containing four to six carbon atoms. The key step is the facile /3-elimination step which generates the desired 2-keto-3-deoxy acids as protected enoi 1,4-1actones in excellent yields. Smooth deprotection then leads to the 2-keto-3-deoxyaldonic acids. In the case of the protected o-galactono-l,4-1actone 6 an epimerisation is observed during the elimination process. This enables the synthesis of both 2-keto-3-deoxy-o-hexonic acids with either o-erythro (1) or o-threo (2) configuration in good to excellent yields in only three steps starting with commercially available o-galactono-l,4-1actone (5).
The Journal of organic chemistry, 2007
A chemoenzymatic synthesis of deoxy sugar esters is described. The synthesis is based on the O-alkylation of carboxylic acid with 2-bromo-5-acetoxypentanal. The method allows treatment of hydroxy carboxylic acids without protection of alcoholic hydroxyl groups. Several stereoisomeric deoxy sugar esters were resolved (up to ee or de > 98%) using a lipase-catalyzed acetylation of hemiacetals that in certain cases afforded deoxy sugar derivatives in the form of aldehydes. The stereochemistry of the reactions was determined by the NMR spectra of mandelic acid derivatives.
An unusual reaction of 1,6-anhydroaldohexopyranose derivatives leading to glycals
Carbohydrate Research, 1985
Treatment of a solution of the 2-O-(NJ+dimethylsulfamoyl) derivative 3 of the levoglucosenone-derived carbocycle 1 in liquid ammonia at-40 to-50" with sodium metal gave 73% of the glycal derivative 4 instead of the expected 2-deoxy derivative (2) of 1. Under the same conditions, the 2-O-(NJ-dimethylsulfamoyl) derivatives of 1,6-anhydro-3,bdideoxy4-C-methyl+-D-ribo-and-arabinohexopyranoses gave, after acetylation, 70% of 6-0-acetyl-1,5-anhydro-2,3,4trideoxy-4-C-methyl-D-erythro-hex-l-enitol. In contrast, the 2-(N,N-dimethylsulfamates) obtained from 1,6-anhydro-3,4-O-isopropylidene-P_D-galacto-and-tale-pyranose gave 6-O-acetyl-l,!i-anhydro-2-deoxy-3,4-O-isopropylidene-o-lyxohex-1-enitol in only low yields; the oxy substituent at C-3 may interfere with the reaction leading to the glycal. RESULTS AND DISCUSSION Numerous procedures for the deoxygenation of secondary alcohols have been developed over the past several years; these include detosyloxylation with lithium
The Journal of Organic Chemistry, 1993
A new deoxygenation-carbonyl addition reaction mediated by samarium(I1) iodide (SmI2) in THFI HMPA was examined with carbohydrate lactones and several substrates containing an a-alkoxy carboxylic ester. In a single reaction, these compounds were deoxygenated and subsequently coupled to several ketones by a carbonyl addition reaction. The first reactions studied simple ester and ketone adducts which were later elaborated to more complex optically active carbohydrate lactones appended to terpene ketones. Simple esters smoothly afforded @-hydroxy carbonyl products. Fully benzoate-protected 3-deoxycarbohydrate lactones were reacted with simple ketones to produce Czbranched sugars. The attendant carbonyl addition to the least sterically hindered face of the aldonolactone provided the major products. Moderate diastereoselectivities (up to 5:l) were observed in the simple ketone products as determined by difference NOE studies. Finally, the terpene ketones, (-1-menthone or (+I-dihydrocarvone, were coupled to 3-deoxycarbohydrate lactones which gave C2branched sugars with very high diastereoselectivities (up to 99:l).
Synthesis of deoxy derivatives of the glucosinolates glucotropaeolin and glucobrassicin
Carbohydrate Research, 1995
The syntheses of 3,4,6-tri-O-acetyl-2-deoxy-l-thio-D-arabino-hexopyranose, 2,4,6-tri-O-acetyl-3-deoxy-1-thio-fl-D-ribo-hexopyranose, 2,3,6-tri-O-benzoyl-4-deoxy-1-thio-fl-D-xylo-hexopyranose, and 2,3,4-tri-O-acetyl-6-deoxy-l-thio-fl-I>-glucopyranose are reported. These thiols were coupled with phenylacetohydroximoyl chloride or indol-3-ylacetohydroximoyl chloride, respectively. Sulfation and subsequent deprotection yielded the corresponding deoxy derivatives of glucotropaeolin and glucobrassicin, two major representatives of the glucosinolate family.