Deoxy‐nitrosugars 8th communication Convenient preparation of 1‐C‐nitroglycosyl chlorides. Halonitro ethers from hydroxy oximes

Abstract

SummaryPartially protected 4-or 5-hydroxy-sugar oxinies were transformed into 5-or 6-membered 1-C-nitroglycosyl chlorides, respectively, by reaction with NaOCl under phase-transfer conditions. With the exception of the oxidation of the gluco-derivative 1 giving the anomers 6 and 7, the reactions were completely diastereoselective. We report a convenient preparation of protected 1-C-nitroglycosyl chlorides directly from the corresponding sugar oximes which should facilitate investigations of the reactivity of halonitro ethers. The oxidation of 4-or 5-hydroxy-sugar oximes to lactone oximes very probably occurs via the tautomeric cyclic hydroxylamines. It should proceed easily also with NaOCl as oxidant. Since Corey & Estreicher [4] have described a two-step one-pot transformation of oximes into chloronitro compounds by oxidation first with HOCl in a biphasic system at pH 5.5 and then with NaOCl in a biphasic system at pH 10 in the presence of a phase-transfer catalyst, a direct oxidation of appropriate hydroxy oximes to chloronitro ethers appeared feasible. In the event, treatment of the D-gluco-and D-manno-configurated 5-hydroxy oximes 1 and 2, respectively, with NaOCl in a biphasic system at pH 11-12 in the presence of a phase-transfer catalyst gave the corresponding chloronitro ethers 6-8 in a good yield (Scheme). The 4-hydroxy oximes 3 and 4 were transformed by a similar treatment first at a pH of ca. 7 and then at pH 11-12 into the chloronitro ethers 9 and 10, respectively, while the dihydroxy oxime 5 gave the novel nitroacetal 11 by double neighbouring-group participation. With the exception of the oxidation of the D-gluco oxime 1 giving a 1 : 1 mixture of 6 and 7, the reactions were completely diastereoselective. The anomeric configura-') 7th Communication: [l]

Deoxy‐nitrosugars. 11th Communication. Reactions of 1‐C‐nitroglycosyl halides and 1‐C‐nitroglycosyl sulfones with dialkyl‐phosphite anions: Nucleophilic attack vs. single‐electron transfer

“…[a]:: = +42.6" (c = 1.12). IR: 2985s, 2938m, 2900m,145Ow, 1444w, 1383m, 1373s, 1260s, 115Os, 1080s, 1025s, 980s, 890m, 852m, (23). A soh.…”

“…Usual workup afforded an oil, which was purified by chromatography (20 g SOz, AcOEt/hexane 1:l) to give 135 mg (48%) of 17. Diethyl (2,3:5,6-Di-O-isopropylidene-l-nitro-a-~-mannofuranosyl) (23). A soh.…”

“…Furthermore, a -alkoxyphosphonates may be preparatively useful in so far as they allow an inversion of polarization at the anomeric centre [20] [21]. Scheme 1 4 X = CI, Br, S0,Ph 5 6Our plan for the synthesis of glycosylphosphonates 6 (Scheme I ) was based on the expectation that the reaction of dialkyl-phosphite anions with geminal chloro-or arylsulfonyl-nitroalkanes reported by Russell and Hershberger [22] to give a -nitro-alkylphosphonates is applicable to the corresponding anomeric nitro-ether derivatives 4 of aldoses, which are readily available [23]. This expectation stems from the observation that the reaction reported in [22] follows a free-radical chain mechanism, which also seems to operate in the reaction of anomeric geminal chloronitro derivatives of aldoses with some weakly basic carbanions [24].…”

Synthesis of glycosyl phosphonates and related compounds

“…We expected that the reaction of dialkyl phosphite anions with halonitroalkanes and 1 -nitrosulfones reported by Russell and Hershberger [7] to give 1-nitrophosphonates [8] would proceed similarly with halonitroethers, which we knew to undergo SRNl reactions with weakly basic carbanions [9]. As tert nitroethers are smoothly reduced [lo] and as halonitroethers of type 7 are easily available from the corresponding aldose oximes [4,111, the proposed sequence seemed promising. In fact, dialkyl phosphite attacked the nitro group of the bromonitroribose 7a (Scheme 2) [12].…”