Lead acetate Mannitol

Optically pure glyceraldehyde acetonides are widely used in the synthesis of enantiomerically pure compounds (EPC synthesis).1 2 3 4 5 Whereas D-(R)-glyceraldehyde acetonide is easily obtained from the inexpensive D-mannitol,6 7 there are only a limited number of practical syntheses of the enantiomeric L-(S)-glyceraldehyde acetonide.8 9 Difficulties arise from different sources 1) availability of the starting material diisopropylidene-L-mannitol 2) length of the synthesis 10 3) nature of the reactants used mercury acetate, mercaptans, lead tetraacetate, ozone at -78°C, 4) moderate yields.11 14... 

Interest has focused on derivatives of mannitol hexanitrate (14) as potential explosives because although this nitrate ester is a powerful explosive it has some property characteristics of a primary explosive. Treatment of mannitol hexanitrate (14) with pyridine or ammonium carbonate " in aqueous acetone leads to a very selective denitration with the formation of mannitol-1,2,3,5,6-pentanitrate (77). Marans and co-workers synthesized the acetate (78), the propionate (79), and the phenylacetate (80) derivatives of mannitol-1,2,3,5,6-pentanitrate and all have significantly lower melting points than mannitol hexanitrate. The incorporation of such groups can also help to increase the solubility of an explosive in the melt of another explosive. 

Another example of solvolysis of a sulfonate has been described by Buchanan and coworkers 90 it occurs without acid, but utilizes a highly polarizable sulfonic ester group. Solvolysis of methyl 2-0-(p-nitrophenylsulfonyl)-a-D-glucopyranoside (84) in water in the presence of sodium acetate for 6 hours at 100° leads, after reduction of the reaction mixture by means of sodium borohydride, to a fraction identified as 2,5-anhydro-D-mannitol (85). This reaction, which... 

Oxepane (seven-membered) rings (1,6-anhydrohexitols)52 have been prepared from the 3,4-isopropylidene acetals of D-mannitol, D-glucitol, and L-iditol, by way of alkaline hydrolysis of the corresponding 1,2 5,6-dianhydrides. The ring structures of the products were established through periodate oxidation and lead tetraacetate oxidation the requisite amount of formic acid was produced, and 3 equivalents of lead tetraacetate were consumed. No inversions at any of the asymmetric centers were involved in the reactions conducted, so the oxepanes had retained the configurations of the starting hexitols. 

Cognate preparation. (R)-2,3-0-Isopropylideneglyceraldehyde. To a solution of l,2 5,6-di-0-isopropylidene-D-mannitol (50 g, 0.19mol, Expt 5.114) in dry benzene (500 ml) (CAUTION) is slowly added lead tetra-acetate (90 g, 0.2 mol) with stirring. After 3 hours the mixture is filtered, and the filtrate concentrated below 25 °C to a syrup from which four 30-ml portions of carbon tetrachloride are evaporated at a temperature maintained below 25 °C. The syrup is distilled in vacuo. The first few millilitres are discarded and the main fraction is collected, 34 g (68%), b.p. 31 °C/5mmHg (1). 

Some related iV-aryl compounds were examined in model experiments in connection with lead tetraacetate cleavage of samandarin derivatives.194 Oxidation in aqueous acetic acid at 60-70° of 1 -deoxy-1-(p-toluidino)-l-arabinitol (LXXXV) and -D-mannitol yielded two moles of formaldehyde per mole, one mole being derived from the terminal carbinol group and the second from subsequent hydrolysis of the Schiff base (LXXXVI) pro-... 

Reeves88 that a benzylidene-l,4-anhydro-D-mannitol rearranges in this solvent. The use of lead tetraacetate in glacial acetic acid at a high temperature led Pizzarello and Freudenberg61 to assign an incorrect structure to a-diisopropylidene-dulcitol, as was shown by Hann, Maclay and Hudson.86... 

Treatment of the monoethylidene-D-mannitol with lead tetraacetate or periodate resulted in the consumption of two molecular equivalents of oxidant with the concomitant production of one mole of formaldehyde, one mole of formic acid and a monoethylidene-D-erythrose, the latter being identified by its conversion into the known crystalline D-erythrosazone.118 This evidence limited the choice of structure for the mannitol acetal to the 1,3- and 2,3-compound (4,6- and 4,5- are the respective identical structures). Two additional facts eliminated the latter alternative, first, the tetratosyl ester gave only one mole of sodium p-toluenesulfonate when heated with sodium iodide in acetone, and secondly, the same monoethylidene-D-mannitol was obtained from the above 1,3,4,6-diethylidene-D-mannitol by acidic hydrolysis.118 For these reasons Bourne, Bruce and Wiggins118 assigned to the mono-, di- and tri-ethylidene-D-mannitols, respectively, the 1,3-, 1,3 4,6- and 1,3 2,5 4,6- structures. 

The extension of the reaction with sodium iodide to tosyl derivatives of other acetals of iditol, glucitol, and mannitol could provide evidence for the conformation of 2,4 3,5-diacetals of mannitol and, more important, lead to a clarification of the steric requirements of this reaction. The importance of 2,4 3,5-diacetals of talitol, at present unknown, is now clear they will have one axial and one equatorial terminal group (see LIU), and the trans ring junction imposes a rigidity of conformation greater than that of any of the diacetals with cis junctions. 

Acetalization of D-mannitol (E) with acetone leads to the preferential blocking of the two terminal 1,2-diol moieties. ... 

The next few steps including the vital palladium-catalysed cyclisation revealed a problem in this synthesis and it is continued in the workbook. An improved synthesis by Trost uses two alkynes in the cyclisation and the problems disappear. This starts from protected mannitol 106 and the oxidative cleavage is followed at once by imine formation 193. Addition of the lithium derivative 194 goes with good selectivity (13 1 in favour of 195). Adjustment of protecting groups and hydrolysis of the acetal leads to the key intermediate37 197. 

R) -1 sopropylideneglycerol is a useful C3-synthon in the synthesis of (S)-P-blockers, e. g. (S)-metoprolol. Also, (R)-isopropylideneglyceric acid may be used as the starting material for the synthesis of biologically active products. The resolution is carried out by selective microbial oxidation of the (S)-enantiomer (Fig. 19-9). The chemical synthesis of (R)-isopropylideneglycerol starts either from unnatural L-mannitol or from L-ascorbic acid (Fig. 19-10). In comparison to the biotransformation, here stoichiometric quantities of lead tetra acetate are needed. 

Lactic acid is mainly prepared in large quantities (around 200 kT per year) by the bacterial fomentation of carbohydrates. These fermentation processes can be classified according to the type of bacteria used (i) the hetero-fermentative method, which produces less than 1.8 mol of lactic acid per mole of hexose, with otho- metabolites in significant quantities, such as acetic acid, ethanol, glycerol, mannitol and carbon dioxide (ii) the homo-fomentative method, which leads to greater yields of lactic acid and lower levels of by-products, and is mainly used in industrial processes [3]. The convo-sion yield from glucose to lactic acid is more than 90 per cent. 

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