Dimethyl 4-tartarate

Proton donors are known to exert considerable influence on the regiochemical and stereochemical outcome of several Sml2-mediated reactions. Yoshida and Mikami (1997) have reported the effect of proton source in the reduction of propargylic phosphates by Palladium(0)/Sml2/proton source system (eq. (42), table 1). The use of 2-methyl-2-propanol as the proton source results in the exclusive formation of allenes, while the diol, dimethyl tartarate ((+)-DMT) gave the alkyne as the major product. 

L-dihydroxy-succinic acid (L(dexiro)-tartaric acid, CXIII). This result establishes the position of the double bond between C4 and C5 and demonstrates that C4 carries only one hydrogen atom while C5 has attached to it the enolic hydroxyl group. Treatment of the enol CXI with ethereal diazomethane gives 5-methyl-A4-D-glucosaccharo-3,6-lactone methyl ester (CXIY) which upon further methylation with silver oxide and methyl iodide yields 2,5-dimethyl-A4-D-glucosaccharo-3,6-lactone methyl ester (CXV). When the latter is subjected to ozonolysis there is formed oxalic acid and 3-methyl-L-threuronic acid (CXVI). Oxidation of this aldehydic acid (CXYI) with bromine gives rise to a monomethyl derivative (CXVII) of L-ilireo-dihydroxy-succinic acid. 

Copper compounds are used routinely and widely to control freshwater snails that serve as intermediate vectors of schistosomiasis and other diseases that afflict humans (Hasler 1949 NAS 1977 Rowe and Prince 1983 Winger etal. 1984 Al-Sabri etal. 1993). These compounds include copper sulfate, copper pentachlorophenate, copper carbonate, copper-tartaric acid, Paris green (copper arsenite-acetate), copper oxide, copper chloride, copper acetyl acetonate, copper dimethyl dithiocar-bamate, copper ricinoleate, and copper rosinate (Cheng 1979). Also, many species of oyster enemies are controlled by copper sulfate dips. All tested species of marine gastropods, tunicates, echinoderms, and crabs that had been dipped for 5 seconds in a saturated solution of copper sulfate died if held in air for as little as a few seconds to 8 h mussels, however, were resistant (MacKenzie 1961). 

In principle, separation of resonances of diastereomeric compounds (such as dl and meso isomers) may be increased simply through use of an appropriate achiral solvent. Chiral solvents may in some cases be especially effective in producing a separation, particularly if the diastereomers differ in configuration about a center that is amenable to analysis by the CSA method. Kaehler and Rehse (89) give a detailed account of conditions necessary for measurement of the ratio of meso- and dZ-tartaric acid employing A,N-dimethyl PEA. Bomyl acetate used as solvent for l,2-difluoro-l,2-dichloroethane (90) allows measurement of the diastereomeric composition. Paquette and co-workers (91,92), using TFAE, were able to determine the diastereomeric purity of the recrystallized adducts 47 of... 

Y,A, -Dimethyl-l,2-bis[3-(trifluoromethyl)phenyl]-1,2-diaminocthanc, prepared in two steps from 3-trifluoromethylbenzaldehyde65, can be easily resolved with tartaric acid and reacted with aldehydes at room temperature to give imidazolidines. 

More recently, Mukai and Hanaoka have demonstrated that a variety of optically active bicyclo[4.3.0]-nones are prepared from the substrates possessing pre-existing stereogenic centers. The precursors are prepared from such a natural chiral pool as dimethyl L-tartarate or L-ascorbic acid (Equation (15)) S2,52a,52b... 

In view of this background, we developed a new chiral auxiliary to allow for the first time the efficient asymmetric a-alkylation of sulfonamides [90]. After testing some amine auxiliaries mainly based on proline, which did not show high diastereoselectivities, we synthesized the 4-biphenyl-substituted 2,2-dimethyl-l,3-dioxan-5-amine 108 as a new auxiliary. The racemate obtained according to Erlenmeyer s phenylserine synthesis was resolved with tartaric acid to give both enantiomers. 

N,N Dimethyl N,N -dinitro-tartramide Dinitrate 1,6-Dimethyl-3,4 dinitroxy- tartar-1,6-dinitramide or l,6-Dimethyldinitramino 3,4-dinitroxy-tartaric Acid, H3G(P2N)N.0C.CH(0N02>.CH(0N02).C0.-KN02).CH3 mw 356.17, N 23,60%, OB to C02 minus 18% crysts, mp 114° bp expl at 117° when heated at the rate of 20° per minute sol in acet, benz, chif, CCI4, and ale. It can be prepd by dissolving NjN -dimethyl-tartramide in acet at below 0° and adding to it. coned nitric acid, followed by acetic anhydride... 

Asymmetric hromination of ketals of alkyl aryl ketones,l a-Bromination of the ketals of alkyl aryl ketones obtained with the dimethyl esters of (2R,3R)- or (2S,3S)-tartaric acid is highly diastereoselective. Hydrolysis of the products provides optically active 2-bromo ketones. 

Diethyl tartrate is the best tartaric acid derivative for enantioselective oxidation of thioethers. This finding was established for the asymmetric oxidation of methyl p-tolyl sulfide with cumene hydroperoxide, that is, 96% ee (DET) 87% ee (diisopropyl tartrate) 62% ee (dimethyl tartrate) [24] and 1.5% ee (bis A, V-dimethy I tart rami de, r-BuOOH as the oxidant) [17]. 

Diastereoselective alkylation of tartaric acid. The enolate (2) of the acetonide of dimethyl (R, R)-tartrate (1) can be generated with LDA in THF-HMPT at — 70° and is sufficiently stable for alkylation with allyl and benzyl halides, but not with other simple alkyl halides, and for addition to acetone (60% yield). The main products (3) of allylation and benzylation have the /ranr-configuration, and thus the substitution occurs with retention of configuration.7... 

Computational efforts to describe the conformational preferences of (R,R)-tartaric acid and its derivatives - mainly for isolated molecules - were made recently [18-25]. The conformations of these molecules also attracted attention from experimental chemists [22-40]. (/ ,/ [-tartaric acid and its dimethyl diester were observed in crystals, in conformations with extended carbon chain and planar a-hydroxy-carboxylic moieties (T.v.v and Tas for the acid and the ester, respectively) [25-28] (see Figure 2). The predominance ofthe T-structure was also shown by studies of optical rotation [31], vibrational circular dichroism (VCD) [23], Raman optical activity [32, 35], and nuclear magnetic resonance (NMR) [22, 33, 34]. The results of ab-initio and semiempirical calculations indicated that for the isolated molecules the Tsv and T as conformers were those of lowest energy [22, 21, 23, 25]. It should be noted, however, that early interpretations of NMR and VCD studies indicated that for the dimethyl diester of (/ ,/ [-tartaric acid the G+ conformation is favored [36-38]. 

Cotton etal. [14] described an asymmetric synthesis of esomeprazole. Esomeprazole, the (S)-enantiomer of omeprazole, was synthesized via asymmetric oxidation of prochiral sulfide 5-methoxy-2-[[(4-methoxy-3,5-dimethyl pyridin-2-yl)methyl]thio]-lH-benzimidazole 1. The asymmetric oxidation was achieved by titanium-mediated oxidation with cumene hydroperoxide in the presence of (S,S)-diethyl tartarate (DET). The enan-tioselectivity was provided by preparing the titanium complex in the presence of sulfide 1 at an elevated temperature and/or during a prolonged preparation time and by performing the oxidation of sulfide 1 in the presence of amine. An enantioselectivity of 94% ee was obtained using this method. 

There is abundant information to support the contention that the lower-melting monoisopropylidene-mannitol (m. p. 85°) is the 3,4-derivative. For example, its tetrabenzoate is identical with that obtained by acetonation of 1,2,5,6-tetrabenzoyl-mannitol,11498 the structure of which is based on independent evidence.114 The larger fragment resulting from the oxidative scission of the D-enantiomorph of the isopropylidene-man-nitol with lead tetraacetate is 2,3-isopropylidene-D-//treo-dihydroxy-succinic dialdehyde, characterized by its subsequent conversion into D-i/ireo-tartaric acid.126 When methylated and hydrolyzed, the L-enantio-morph of the monoketal affords a tetramethyl-mannitol, which, in turn, yields dimethyl-L-glyceraldehyde with lead tetraacetate.127 Each of these facts is in itself proof that the acetone residue occupies the 3,4-position in the mannitol molecule. 

Since dimethyl sulfate decomposes rapidly in concentrated alkaline medium, addition of the powdered tartaric acid amide must begin immediately after the dimethyl sulfate is introduced. The amide should be added as fast as possible (ca. 20-30 min) within the limits of the capacity of the reflux condenser and the mechanical stirrer. The amount of dimethyl sulfate can be increased up to 2.5 equivalents and fresh benzyltriethyl-ammonium chloride can be added toward the end of the addition. With less rapid addition and stirring, the yield drops to 45-55%. 

---