Ethyl d,/-lactate

Discuss possible procedures for resolution of ethyl D,L-lactate (ethyl 2-hy-droxypropanoate bp 155°) into ethyl d-lactate and ethyl L-lactate. 

Baiker and colleagues have extensively studied the heterogeneously catalyzed asymmetric hydrogenation of ethyl pyruvate, giving ethyl D-lactate, in the presence of compressed gases [Eq. (20)] (98,99,108,109) ... 

The properties of cesium salts can be taken advantage of to convert (5)-ethyl lactate to its / -enantiomer without racemization [63]. Treatment of mesylate 156b with cesium propionate gives (7 )-(acyloxy)propionate (170) in good yield [72]. Titanium-mediated transesterification of the ( S)-enantiomer of 170 under essentially neutral conditions has been reported to give ethyl L-lactate (60% yield) with no racemization [64]. Application of this methodology to (/ )-170 should give ethyl D-lactate (171). 

A series of cyanoacetic acid derivatives 96 (94TA1435, 95TA255) was used for the introduction of a chiral moiety into position 3 of a pyran ring Oppolzer s sultam (a), (—)-menthol (b), (IS)-endo-(-)-borneol (c), ethyl (S)-(—)-lactate (d), diisopropylidene-o-glucofuranose (e). Both Methods 1 and... 

Optically active amino acids The NCS-promoted rearrangement of allylic phenyl selenides (12,121) when applied to an optically active substrate (1), available from ethyl (S)-lactate, results in an allylic amine (2), which can be converted into an optically active N-protected D-amino acid (3) in 78-84% ee. 

Rhlid el a I.2 4 have tried to exploit these results technologically by preparing 2-(l-hydroxyethyl)-2-thiazoline by microbial fermentation (cysteamine, ethyl L-lactate, and D-glucose with bakers yeast) and incorporating it into a pizza recipe (5 mg per 50 g raw dough), leading to increases in the roasted, toasted, popcorn-like aromas. 

D-lactate dehydrogenase and, 271 lipoamide dehydrogenase and, 126 NADH dehydrogenase and, 206 succinate dehydrogenase and, 247 thioredoxin reductase and, 147, 148 Ethyl hydrogen peroxide, catalase and, 391-392, 395 iV-Ethylmaleimide c> tochrome b, reductase and, 163,... 

D-Digitoxose, a component of cardiac glycosides found in Digitalis purpurea and other higher plants, can be prepared following a similar method starting from ethyl (7 )-lactate and (7 )-HYTRA [83] (Scheme 13.41). 

K)-108 is isolated in 42% overall yield and > 99% ee. This compound has been converted into 109 by iodolactonization. It is a precursor of all kinds of 2-deoxyfuranosides [246], D-Digitoxose, a component of cardiac glycosides found in Digitalis purpurea and other higher plants, can be prepared following a similar method starting from ethyl (i )-lactate (111) and (i )-HYTRA (O Scheme 50) [247],... 

Cycloaddition of Af,Ar-fumaroyldi[(2/ )-bornane-10,2-sultam] 32 to cyclopentadiene (2) proceeds with excellent diastereoselectivity affording adducts 33 and 34 with a d.r. [(55,65)/ (5f ,6i )] >98 2 and in very good yields (80-95 %). In contrast to ethyl (5)-lactate and (5)-pro-line fumarates the d.r. value is almost independent of the amount of equivalents of TiCl4 used... 

A related family of 3-amino-2,3,6-trideoxyhexoses, L-daunosamine (386), the carbohydrate component of anticancer anthracycline antibiotics, L-vancosamine (387), the carbohydrate component of the antibiotics vancomycin and sporaviridin, and D-ritosamine (388), the enantiomer of the carbohydrate component of the antibiotic ristomycin, has been prepared from ethyl L-lactate [119]. 

Hydrolysis reaction of ethyl d- and L-lactates (EtLa)s catalyzed by protease were studied EtLLa was consumed a little faster than EtDLa. The mechanism of the protease-catalyzed oligomerization was similar to that of lipase (as seen in Figs. 3 and 4), but in an L-selective manner the enantioselection is governed by the deacylation step. 

The enantiomerically pure vinylic organolithium reagent 8 is prepared from (A )-ethyl lactate in four steps. Subsequent addition of A-mesitylsulfonylimines 7 (they provide better diastereo-selectivilies than the corresponding jV-Losylimines) at — 110°C in tetrahydrofuran affords the adducts 9a and 9b in moderate yields (20-63%) but high diaslereoselectivities (d.r. 96 4 — 98 2)l0. 

When the above-mentioned ring expansion with diazomethane 74) of trimethyl-dioxo[2.2]metacyclophane 65 (methylation was necessary to increase the inversion barrier to > 130 kJ) was performed in the presence of optically active alcohols at —60 °C, asymmetric induction occurred to an extent of ca. 40% ee (enantiomeric excess as determined by nmr-spectroscopy in the presence of chiral shift reagents)85). (+)-DibutyI tartrate favoured the dextrorotatory diketone 66 ([a]D 160° for the optically pure product) — the isomeric 67 was formed only with 3% ee (—)-ethyl lactate on the other hand led to an excess of (+)-67 ([a]D +240°) but gave (+)-66 with only 10% ee85). 

The results collected in Table 5 suggest that hydrocarbon residues, especially aromatic groups, in the solvent are strongly responsible for the interaction with cis-(1+4). The position of the largest hydrocarbon residue apparently determines whether P- or M-[6]-helicene will be formed in excess. Replacement of the methyl group in (S)-ethyl lactate (b) by a phenyl group giving (S)-ethyl mandelate (d), increases the optical yield fivefold. 

Ethyl lactate and derivs (cont d) ethyl lactate nitrate 6 E306—E307 ethyl-2 (or 3)-nitrolactate nitrates 6 E307... 

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