Threitol hydrolysis

D. 1,4-Di-O-benzyl-L-threitol. The crude ketal is dissolved in methanol (300 mL), 0.5 N hydrochloric acid (30 idL) is added, and the resulting mixture Is heated to reflux. Acetone and methanol are slowly distilled off (Note 29). Additional methanol (50 mL) and 0.5 N hydrochloric acid (20 mL) are added and the mixture Is kept at room temperature until ketal hydrolysis Is complete. The mixture Is diluted with saturated sodium bicarbonate solution (500 mL) and extracted with ether (3 x 500 mL). The ether extracts are combined, dried over anhydrous magnesium sulfate, and filtered. Removal of volatile material under reduced pressure gives crude l,4-di-0-benzy1-L-threitol as a pale yellow solid. This solid is recrystallized twice from chloroform/hexanes, to provide 59-65 g (195-215 mmol, 57-63% yield) of pure diol, up 54-55 C (Notes 30 and 31). Concentration of the mother liquors from the recrystallizations gives a yellow solid which is chromatographed on 70-230 mesh silica gel 60 (500 g) (Note 32), and eluted with 50% ethyl... 

The Smith analysis discussed at the beginning of this Section gives little information on the presence or absence of (1 — 6)-linkages. If, however, the polyalcohol is methylated before hydrolysis, mixtures of mono- and di-methylglycerols and erythritols (or threitols) may be obtained.807,830,631 This method was clearly explained by Bahl and... 

Benzylidene-D-threitol (VII) was prepared by Haskins, Hann and Hudson79 by hydrogenation of 2,3-benzylidene-D-threose, a product of the periodate oxidation of 2,3-benzylidene-D-arabitol. The tetritol was proved to be D-threitol, rather than erythritol, by the fact that hydrolysis of VII and subsequent treatment with benzaldehyde afforded the known dibenzylidene-D-threitol. The acetal group was allocated to the 2,3-position on the basis of independent evidence concerning the structure of the parent benzylidene-D-arabitol (see page 152). For the physical constants of acetals of threitol see Table VIII. 

The formation of nonseparable mixtures of diastereomers in the asymmetric cyclopropanation of homochiral cycloalk-2-enone 1,4-0-benzyl-L-threitol acetals with the Simmons-Smith re-agent has been circumvented by acetalizing with ( —)-(5, S)-hydrobenzoin. Treatment of (5,5)-hydrobenzoin acetals with Simmons-Smith reagent in refluxing diethyl ether provided good yields of cyclopropane acetals with a diastereoselectivity of > 13 1 (Table 2). The products were recrystallized from anhydrous diethyl ether to give diastereochemically pure products. Hydrolysis of the acetals afforded enantiomerically pure cyclopropyl ketones. Since hydrobenzoin is available in both enantiomeric forms, either enantiomer of a particular cyclopropyl ketone can be prepared via this methodology. ... 

The structure of tetrasaccharide 76 was proved by oxidation with periodate. The products obtained were reduced with sodium boro-hydride, and the reduction products were cleaved by hydrolysis 2-amino-2-deoxy-D-galactose, erythritol, a threitol, and glycerol were isolated. 

The presence of galactofuranose residues in SXA was shown by controlled, periodate oxidation, reduction with borohydride, and mild hydrolysis (with acid) to yield arabinose. Sequential periodate oxidation, reduction with borohydride, and acidic hydrolysis of SXA yielded threitol phosphates. 

Trifluoroacetic acid hydrolysis of the isopropylidene protecting group in 79 without loss of the tosyl group provides (25,3 5)-1-0-tosyl-L-threitol (116), which can be cyclized with basic resin to afford (25,3 S)-l,4-anhydro-L-threitol (117) in good overall yield. Treating 117 with triphenylphosphine in pyridine affords the chiral diphosphinite diphin (118), which has been utilized as a ligand in asymmetric hydrogenation, hydrocyanation, and hydroformylation reactions [48] (Scheme 26). 

The diversity associated with silyl protecting groups as well as the chemical conditions available for their removal makes them attractive alternatives to benzyl protection of the hydroxy groups of either D- or L-tartaric acid derivatives. O-isopropylidene-L-threitol (37) is mono-protected with er -butyldimethylsilyl chloride to furnish 266, which is converted in three steps to the nitrile 267. Reduction with DIBAL and Wittig olefination followed by desilylation with fluoride and Swern oxidation of the resulting alcohol provides aldehyde 268, which reacts with methyl 10-(triphenylphosphorane)-9-oxo-decanoate (269) to afford enone 270. Reduction of 270 with subsequent preparative TLC and acetal hydrolysis furnishes (9R)-271 and (9 S)-272, both interesting unsaturated trihydroxy Cig fatty acid metabolites isolated from vegetables [91] (Scheme 62). 

Intramolecular iodoamidation of pentenetriol derivative 52, obtained from L-threitol derivative 51, was used to prepare (-)-anisomycin in 17 20% overall yield (Scheme 6) [61]. Oxidation of 51 [62], followed by methylenation, acid hydrolysis, and protection with CCI3CN gave the olefin 52, whose reaction with iodine in the presence of sodium bicarbonate gave a 4.5 1 mixture of 53 and 54. Hydrolysis of the mixture, followed by N-protection with B0C2O afforded a 12 1 mixture of 55 and 56. On the other hand, when 52 was reacted with iodine monobromide in the presence of potassium carbonate, compound 53 only was obtained that could be transformed into a 37 1 mix-... 

The chirality induced in styrene-containing co-polymers (post-glycosidic hydrolysis) as a consequence of using carbohydrate-bearing monomers (L-threitol, a-D-... 

Cholesteric polyesters were prepared from silylated derivatives of 2,3-di-(9-isopropylidene-D-threitol, DAS, or DAM with dicarboxylic acid dichlorides by polycondensation in solution [34]. Trifluoroacetic acid-water allowed an easy cleavage of the isopropylidene group without hydrolysis of the polyester. All these polyesters formed a broad cholesteric phase, and the polymers containing 5 or 10 mol per cent sugar diol displayed a blue Grandjean texture. 

A method for the electrochemical reduction of D-xylose to 2-deoxy-D-r/rr o-pentitol has been described. The homogeneous hydrogenation of sugars using tris-triphenylphosphine ruthenium chloride is improved in the presence of hydrogen chloride, which inhibits competitive decarbonylation of the sugar. L-(2,3)-Threitol is easily prepared from ( + )tartaric acid by lithium aluminium hydride reduction of the 2,3-0-isopropylidene derivative of diethyl tartrate, followed by acid hydrolysis of the resultant ketal. ... 

An efficient conversion of L-threitol to its 1,3 2,4-di-0-methylene derivative by use of formaldehyde and HBr, followed by Amberlyst 15 and 4A molecular sieves, has been reported. 3,5-0-Ethylidene-(1) and 3,5-0-isopropylidene-D-glucitol (2) have been prepared, as shown in Scheme 1, in mediocre and good yield, respectively both compounds were thermodynamically unstable and very sensitive to hydrolysis. Improved yields have been claimed in the syntheses of isopropylidene saccharides with acetone in the presence of molecular sieves and toluenesulfonic or methanesulfonic acid. 

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