Enzymatic hydrolysis, dimethyl

Other approaches to (36) make use of (37, R = CH ) and reaction with a tributylstannyl allene (60) or 3-siloxypentadiene (61). A chemicoen2ymatic synthesis for both thienamycia (2) and 1 -methyl analogues starts from the chiral monoester (38), derived by enzymatic hydrolysis of the dimethyl ester, and proceeding by way of the P-lactam (39, R = H or CH ) (62,63). (3)-Methyl-3-hydroxy-2-methylpropanoate [80657-57-4] (40), C H qO, has also been used as starting material for (36) (64), whereas 1,3-dipolar cycloaddition of a chiral nitrone with a crotonate ester affords the oxa2ohdine (41) which again can be converted to a suitable P-lactam precursor (65). 

The thiono derivatives of tetrahydro-1,3-oxazine became a subject matter of some interest since Kjaer and Jensen discovered that products of enzymatic hydrolysis of Malcolma maritima contain 6-methyl- and 6,6-dimethyl-2-thionotetrahydro-l,3-oxazine (26). The authors proved the identity of these compounds with the products of cyclization of 3-hydroxypropyl-isothiocyanate in an alkaline medium. 

Dimethyl sulfide is derived primarily from the enzymatic hydrolysis of dimethylsulfoniopropionate(CH3)2S+CH2CH2COO DMSP),an osmoregulatory compound produced by a wide variety of marine phytoplankton [313,317]. Intracellular DMSP hydrolysis has been shown in phytoplankton [318], in macro algae [319], and also in bacteria following uptake of DMSP from seawater [320]. Reported seawater concentrations of dissolved dimethyl sulfide (< 0.1-90 nM) and DMSP (1 -1000 nM) vary with increasing depth, spatially from coastal areas to the open ocean, and also temporally from winter to summer [313-316]. 

The above example clearly points to nonenzymatic hydrolysis of 3,4-dimethyl-5-phenyloxazolidine (11.106). However, enzymatic hydrolysis cannot entirely be ruled out. A related compound, 3-isopropyl-5- [(naphthalen-... 

The stereogenic center at C20 is introduced by enantioselective enzymatic hydrolysis of MOM-protected malonic acid dimethyl ester derivative 60 (Scheme 10) with pig liver esterase (PLE). The asymmetric compound 61 is obtained in 90 % yield and 98 % ee. Amide formation with Mu-... 

This collection begins with a series of three procedures illustrating important new methods for preparation of enantiomerically pure substances via asymmetric catalysis. The preparation of 3-[(1S)-1,2-DIHYDROXYETHYL]-1,5-DIHYDRO-3H-2.4-BENZODIOXEPINE describes, in detail, the use of dihydroquinidine 9-0-(9 -phenanthryl) ether as a chiral ligand in the asymmetric dihydroxylation reaction which is broadly applicable for the preparation of chiral dlols from monosubstituted olefins. The product, an acetal of (S)-glyceralcfehyde, is itself a potentially valuable synthetic intermediate. The assembly of a chiral rhodium catalyst from methyl 2-pyrrolidone 5(R)-carboxylate and its use in the intramolecular asymmetric cyclopropanation of an allyl diazoacetate is illustrated in the preparation of (1R.5S)-()-6,6-DIMETHYL-3-OXABICYCLO[3.1. OJHEXAN-2-ONE. Another important general method for asymmetric synthesis involves the desymmetrization of bifunctional meso compounds as is described for the enantioselective enzymatic hydrolysis of cis-3,5-diacetoxycyclopentene to (1R,4S)-(+)-4-HYDROXY-2-CYCLOPENTENYL ACETATE. This intermediate is especially valuable as a precursor of both antipodes (4R) (+)- and (4S)-(-)-tert-BUTYLDIMETHYLSILOXY-2-CYCLOPENTEN-1-ONE, important intermediates in the synthesis of enantiomerically pure prostanoid derivatives and other classes of natural substances, whose preparation is detailed in accompanying procedures. 

In parallel to the diethyl ester 9 the corresponding dimethyl ester was also tested as an alternative substrate for the enzymatic reaction [28], Compared with 9, however, the enzymatic hydrolysis slowed down to only 44% conversion after 74 hours and afforded the desired monoacid (R)-2b in merely 94% ee along with 6.7% (GC) of the undesired monoacid (corresponding to 16). Consequently, this approach was no longer considered. 

Trisubstituted Epoxides. To date, only a limited set of data are available on the enzymatic hydrolysis of trisubstituted epoxides (Table 11.2-7). Regardless of their steric bulkiness, however, they seem to be accepted by epoxide hydrolases from bacterial1110, 119], fungal[92, 941 and yeast[9S1 sources, as long as the access to one side of the substrate is not too severely restricted (e.g. a 2,2-dimethyl-3-alkyloxirane). Further data are required to depict a general selectivity pattern within this group of substrates. 

Amsberry and Borchardt have applied Cain s cascade concept to prepare lipophilic polypeptide prodrugs. The amine functionality of the polypeptide is coupled to 2 -acylated derivatives of 3-(2, 5 -dihydroxy-4, 6 -dimethyl-phenyl)-3,3-dimethylpropionic acid (Fig. 33.23). Under simulated physiological conditions the parent amine is regenerated in a two-step process enzymatic hydrolysis... 

Hydrolysis can also be accomplished under enzymatic conditions. Dimethyl (5)-malate (2), when incubated with pig liver esterase (400 units per 43 mmol of substrate), is hydrolyzed regioselectively to the optically pure acid 14 [22]. 

The PTT is a eopolymer of 1,3-propanediol and aromatic terephthahc acid or dimethyl terephthalate, which can be synthesized by condensation polymerization. The above precursors for PTT can be derived from both renewable resources like com and non-renewable resources like conventional petrolenm based products. The stmcture of PTT is shown in Figure 12. In its class, it has been observed to be degradable by enzymatic hydrolysis in addition to the thermal degradation So far pristine PTT does not seem to have found apphcations in packaging bnt its blend with LDPE, PP, or PET can be used for packaging applications. 

Human urine (women) Enzymatic hydrolysis of C-labeled of Dimethyl- Recovery Large range in amount Grace et al. ... 

ANTIDIABETIC AND CNS DRUGS ENZYMATIC HYDROLYSIS OF DIMETHYL BICYCLO[2.2.1]HEPTANE-1,4-DICARBOXYLATE... 

Moreover, lignocellulose is not edible and could theoretically be utilized without any impact on food production. The cellulose and hemicellulose fraction of lignocellulose may serve for the production of cellulosic ethanol, which could be produced via acid or enzymatic catalyzed hydrolysis of cellulose, followed by further fermentation to yield ethanol. Alternatively, the whole plant can be gasified to yield syngas, followed by methanol or dimethyl ether synthesis or Fischer-Tropsch technology that produces hydrocarbon fuels. Furthermore, controlled (bio-)chemical transformations to novel fuel compounds based on cellulose, hemicellulose, or lignin are possible, and numerous recent publications emphasize intense research in this direction. 

Bluegill and catfish were both able to hydrolyze DFP, dichlorvos, and dimethyl 2,2,2-trichloro-l-n-butyryloxyethyl phosphonate (butonate). Catfish enzymes were also able to hydrolyze paraoxon and methyl 3-hydroxy-alpha-cronate dimethyl phosphate (mevinphos) although at a very slow rate. Kms calculated for the enzymes of both species indicated that each had a greater affinity for DFP than dichorvos. Sulfhydryl reagents and Cu2+ were found to inhibit the enzymatic activity of both organisms. Paraoxon had no effect. Cleavage products were identified as dimethyl phosphate and 2,2-dichloroacetaldehyde from dichlorovos hydrolysis and diisopropyl phosphate from the hydrolysis of DFP. 

An enzymatic resolution of dimethyl (i , S)-malate with pig liver esterase (PLE) relies on selective hydrolysis of the (5)-diester to monoacid 14, leaving dimethyl (i )-malate (203) behind [10,22]. The reaction is performed at 0 °C in 20% aqueous methanol, and the desired (i )-203 is obtained in 42% yield with 93% ee (maximum theoretical yield 50%). 

Enzymatic 7-ACA splitting procedures [for general review, see 261] have been developed and commercialized by companies like Asahi Chemical, Hoechst, and Novartis. The replacement of the hitherto employed chemical deacylation processes like the imino ether (Figure 1.1-3) or the nitrosyl chloride method [262] resulted in a cost reduction of 80% and a decrease of the waste volume by a factor 100 from 311 to 0.3 tons per 1-ton 7-ACA. Chlorinated hydrocarbons like dimethyl aniline and methylene cloride as well as heavy metal ions can be completely avoided. Instead of zinc salt formation, multiple silylation, formation of the imino chloride, imino ether, and finally an imino ether hydrolysis, the side chain is removed in two enzymatic steps (Figure 1.1-3). 

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