A-amino-y-butyrolactone

Few accounts of the reactions of coordinated ligands have been published. One recent report indicates that the copper complex of S-methylmethionine yields the copper complex of a-amino-y-butyrolactone and dimethyl sulfide upon heating.8 ... 

Acetoxy-l-acetylproline, 251 L-a-Amino-y-butyrolactone, 207 /-Butyl hydroperoxide-Dialkyl tar-trate-Titanium(IV) isopropoxide, 51 (Camphorylsulfonyl)oxaziridines, 64 Cumene hydroperoxide-Dialkyl tar-trate-Titanium(IV) isopropoxide, 52 Diisobutylaluminum hydride-Tin(II) chloride-(S)-1 -[ 1 -Methyl-2-pyrroii-dinyl]methylpiperidine, 116 (S)-Phenylglycine, 225 L-Valine, 226 Crown ethers Benzo-14-crown-4, 143 12-Crown-4, 167 12-Crown-6, 218... 

Early syntheses of SeMet were tedious, non-stereospecific or limited to small-scale preparations. Klosterman and Painter (1947), for example, first reacted 5-((3-bromoethyI)- hydantoin with benzyl selenol to yield y-benzylselenoho-mocysteine. The latter was converted to the sodium salt of DL-selenohomo-cysteine with sodium in liquid ammonia, and reacted with methyl iodide to yield DL-SeMet. Plieninger (1950) obtained DL-SeMet by the reaction of sodium selenomethyl mercaptide with a-amino-y-butyrolactone in an inert solvent at 170°C. A synthesis of DL-SeMet from acrolein was also described (Zdansky, 1968). The first stereospecific synthesis of L-SeMet via esters of tosylated homoserine was reported by Pande et al. (1970). 

Plieninger, H. 1950. The cleavage of y-butyrolactone and a-amino-y-butyrolactone with sodium methylmercaptide or selenide. A synthesis of methionine. Chem. Ber. 83, 265-268. 

Method Four, Snyder et al, (736). ct-Oximino-y-bu rrolactone (A) u prepared in 90% yield from acetobutyro-y-l stone and ethyl nitrite in methanol. 3,6-Bis-(j8-hydroxyethyl)-2,5-diketopiperazine (B) is prepared in 60% yield from (A) through a-amino-y-butyrolactone by reduction of the oxime with hydrogen and a palladium catal3rst. 3,6-Bis-(j3-chloroethyl)-2,5-diketopiperazine (C) is prepared in 90% yield from (B) and thionyl chloride. 3,6-Bis-(j8-methylthiolethyl)-2, diketopiper-azine (D) is prepared in 60% yield from (C) and sodium methylmer-captide . DL-Methionine is prepared in 90% 3rield by the HCl hydrolyris of (D). The over-all yield is 26%. 

The direct cleavage of Ado-Met into the thioether and a-amino-y-butyrolactone, which is then converted non-enzymatically into homoserine, is catalyzed by a lyase distributed in prokaryotes and eukaryotesl (pathway 2). 

In addition, other systems of nomenclature for AHLs have also appeared in the literature describing them as derivatives of furanone, y-butyrolactone or 4-butanolide. For example, the above V.fischeri autoinducer can also be named as (S)-N-(3-oxohexanoyl)-3-aminodihydro-2(3H)-furanone,(S)-a-(3-oxohexa-noyl)amino-y-butyrolactone or (S)-2-(3-oxohexanoyl)amino-4-butanolide (another IUPAC name) [27]. 

R1 = R2 = H) gave the triazolo[l,5-a]pyrimidines (125), but with 124 (R1 = R2 = Me) afforded the dioxo derivative 126, and with a-cyano- y-butyrolactones (127) or 2-amino-3-ethoxycarbonyl-5,6-dihydro-4//-thiopyran (129) gave the triazolopyrimidines 128 and 130, respectively (81JHC1287). Treatment of 4-ethoxymethylene-2-phenyl-5(4//)-oxazolone (131) with 5-amino-3-methylthio-l//-1,2,4-triazoles gave the triazolo[l,5-a]pyrimidi-none 132 and the [4,3-a] isomer 133 (93H955) (Scheme 24). 

Amino-y-butyrolactones.5 The (dimethylamino)carbene 1 undergoes highly diastereoselective aldol reactions with aldehydes even in the absence of a Lewis acid to form syn-adducts 2, from which the metal unit can be removed by photolysis. 

The oxidation of the 3-amino-2-(l,2,2-trimethylpropyl)-4(3//)-quinazolinone (3), more easily prepared than (+)-2, with lead tetraacetate in the presence of a-methylene-y-butyrolactone gave the spiroaziridine with very little asymmetric induction40. This is probably due to the competition of secondary attractive interactions between the carbonyl oxygen of the lactone and either the carbonyl or the imine group of the heterocycle. However, the same oxidation carried out in the presence of trifluoroacetic acid (3.4 mol equiv) gave only one diastereomer 440, whose relative configuration was established by X-ray crystallography. 

The substituted imidazo-thiazole, dexamisole, has antidepressant properties and its isomer, levamisole, possesses anthelmintic and immunostimulant properties. Enantiomers of HA-966 (3-amino-l-hydroxypyrrolid-2-one) exhibit distinct central nervous system effects (-b)-HA-966 is a selective glycine/A-methyl-D-aspartate receptor antagonist, but (— )-HA-966 is a potent y-butyrolactone-like sedative. A comparison of (-I-) and (—)-3-methoxycyproheptadine shows that all of the anticholinergic activity of the ( )-3-methoxycyproheptadine resides solely in the dextrorotatory enantiomer, while the antiserotonin activity resides in the levorotatory enantiomer. ... 

Method Three, Livak et ad. (521). a-Bromo-y-butyrolactone (A) is prepared in 80% yield from y-butyrolactone (commercial avmlable), FBr, and bromine. a-Amino-y-hydroxybutyric acid (B) is prepared in 60% yield by amination of (A). 5-()8-Bromoethyl)-hydantoin (C) is prepared in 51% yield by the reaction of (B) with potassium cyanate to give y-hydroxy-a-ureidobutyric acid (D) and by the HBr hydrolyris of (D). 5-(j0-Methylmercaptoethyl)-hydantoin (E) is prepared in 73% yield from sodium methylmercaptide and (C). DL-Methionine is prepared in 95% yield by the Ba(OH)j hydrolysis of (E). The over-all yield is about 17%. 

The unusual amino-acid avenic acid (195), which possesses iron chelating activity has been synthesized from L-a-hydroxy-y-butyrolactone by two independent groups. Stimulated by its value in biosynthetic studies a route to chiral methylvaline has been developed based on an unusual specificity in the hydrogenation of an isopropenyl function using Wilkinson s catalyst. [3- H]Valine has also been prepared for the same purpose. 

Condensation of 3-(2-amino-4-thiazolyl)comnarin 91 with a-acetyl-y-butyrolactone in a mixture of polyphosphoric acid and POCI3 afforded thiazolo[3,2-a]pyrimidin-5-one 92, while condensation of 91 with P-keto esters gave 7-methyl-3 -(2-oxo-2H-chromen-3 -yl)-5 H-[ 1,3]thiazolo [3,2 -a]pyrimidin-5 -ones 93(Scheme 42). Reaction between 91 and diethyl 2-(methoxymethylene)malonate imder solvent-free conditions yielded 3-(2-oxo-2H-chromen-3-yl)-5-oxo-5H[l,3]thiazolo[3,2-a]pyrimidine-6-carboxylate 94 [67],... 

An obvious way to target chiral compounds is to start with a compound in which the chiral center is already present. Here natural products and derivatives offer a rich pool of generally inexpensive starting materials. Examples include L-hydroxy and amino adds. Sometimes, just one out of many chiral centers is predestined to remain, as in the synthesis of vitamin C from D-glucose, or in the preparation of (S)-3-hydroxy-y-butyrolactone from ladose. 

Several recent reviews have included specific types of electrophilic cyclofunctionalization reactions.1 Important areas covered in these reviews are halolactonization u cyclofunctionalization of unsaturated hydroxy compounds to form tetrahydrofurans and tetrahydropyrans lb cyclofunctionalization of unsaturated amino compounds lc cyclofunctionalization of unsaturated sulfur and phosphorus compounds ld lf electrophilic heterocyclization of unconjugated dienes 1 synthesis of y-butyrolactones 1 h synthesis of functionalized dihydro- and tetrahydro-furans lj cyclofunctionalization using selenium reagents lk lm stereocontrol in synthesis of acyclic systems 1" stereoselectivity in cyclofunctionalizations lP and cyclofunctionalizations in the synthesis of a-methylenelactones.lq Previous reference works have also addressed this topic.2... 

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