A-Hydroxyacetals

Glycolic (a-hydroxyacetic) acid [79-14-1J M 76.1, m 81", pK 3.62. Crystd from diethyl ether. 

Hydroxy-L-prolin is converted into a 2-methoxypyrrolidine. This can be used as a valuable chiral building block to prepare optically active 2-substituted pyrrolidines (2-allyl, 2-cyano, 2-phosphono) with different nucleophiles and employing TiQ as Lewis acid (Eq. 21) [286]. Using these latent A -acylimmonium cations (Eq. 22) [287] (Table 9, No. 31), 2-(pyrimidin-l-yl)-2-amino acids [288], and 5-fluorouracil derivatives [289] have been prepared. For the synthesis of p-lactams a 4-acetoxyazetidinone, prepared by non-Kolbe electrolysis of the corresponding 4-carboxy derivative (Eq. 23) [290], proved to be a valuable intermediate. 0-Benzoylated a-hydroxyacetic acids are decarboxylated in methanol to mixed acylals [291]. By reaction of the intermediate cation, with the carboxylic acid used as precursor, esters are obtained in acetonitrile (Eq. 24) [292] and surprisingly also in methanol as solvent (Table 9, No. 32). Hydroxy compounds are formed by decarboxylation in water or in dimethyl sulfoxide (Table 9, Nos. 34, 35). 

Rearrangement of trivalent (5-hexenyl)Co(salen) proceeds via a radical chain process leading to the isomeric cyclopentylmethyl complex.1387 The efficiency with which this rearrangement occurs is dependent on the presence of trace impurities or 02. The selective reaction of alcohols (ROH) with arylglyoxals (ArCOCHO) to give a-aryl-a-hydroxyacetic esters ArCH(0H)C02R is catalyzed by compounds of this family.1388... 

Sonawane et al. (Sonawane et al., 1994) described a practical and efficient synthesis of fenoprofen using commercially available m-phenoxybenzaldehyde as the starting material. The key step in the synthesis is the transformation of the a-hydroxyacetal (i) into its chlorosulfonyl ester in situ and its concomitant rearrangement to the methyl ester (ii) in high yields. The required a-hydroxyacetal (i) can be readily prepared from m-methoxybenzaldehyde by the routine sequence of reactions Grignard reaction with ethyl bromide or chloride, oxidation and finally a-chlorination with CuCI2-LiCI/DMF. 

VI Cohen, RE Gibson, LH Fan, R De la Cruz, MS Gitler, E Hariman, RC Reba. Synthesis and muscarinic cholinergic receptor affinities of 3-quinuclidinyl-l-a-(alkoxyalkyl)-a-aryl-a-hydroxyacetates. J Med Chem 34 2984-2993, 1991. 

At temperatures around 200°, a-hydroxyacetates are transformed to oxiranes via a tautomeric ortho-monoester with neighboring-group participation. By the action of heat. CO2 is split off the carbonic acid esters of 1,2-diols and oxiranes are formed. Disecondary or ditertiary 1,2-diols react with diaryldialkoxysulfurane 66 by antiperiplanar intramolecular nucloephilic displacement via a (3-hydroxy-alkoxysulfonium ion intermediate 67 (Eq. 56). ... 

AcAc-1 (Figure 3) and AcAc-2 (Figure 4) - dimers formed by two molecules of the a-hydroxyacetic acid... 

The name used by Chemical Abstracts for cyclandelate is a-hydroxybenzeneacetic acid, 3,3,5-trimethyl cyclohexyl ester. It is also called mandelic acid, 3,3,5-trimethylcyclohexyl ester 3,3,5-trimethylcyclohexyl mandelate 3,3,5-trimethylcyclohexyl amygdalate and 3,3,5-trimethyl cyclohexanol a-phenyl-a-hydroxyacetate. Trade names include, Cyclospasmol, Natil, Novodil, Perebral, and Spasmocyclon (1). The Chemical Abstracts number is 456-59-7. 

Our first approach [51] to azetidine-2,3-diones relies on the silatropic rearrangement of trimethylsilyl a-hydroxyacetates 87 into the thermodynamically more stable a-trimethylsilyloxyacetic acids 88. The [2 H- 2] cycloaddition step was carried out by means of phenyl dichlorophosphate reagent in yields being in the range 40-65%. Under these conditions, the P-lactam 91 was produced in 45% yield as the single cis isomer. To transform 91 into 93 dimethylbromosulphonium bromide-triethylamine system [52] furnished the desired a-keto P-lactam in 90% yield. 

Aroxyacoxy compds. Bis(hemiacetals), cyclic 1-Carbalkoxyoxonium salts Diacetals, cyclic a-Diketone monoketals Enolperoxides a-Hydroxyacetals... 

PGA for sutures is polymerized from the cyclic dimer of a-hydroxyacetic acid, more commonly called glycolic acid. PGA can be polymerized either directly or indirectly from glycolic acid. For PGA of suture fiber grade (i.e., molecular weight >20 000), ring-opening polymerization of the cyclic dimers of glycolic acid is used. Numerous catalysts are available... 

The carbonylation of epoxides and aziridines has been studied for several decades, and two forms of this process are now well established. Highly active catalysts for the ring expansion of epoxides and aziridines to p-lactones and 3-lactams are now known. In addition, conditions have been developed for the hydroformylation of epoxides to a-hydroxy aldehydes (including protected a-hydroxyacetals), and similar conditions have been developed for the tandem hydroformylation and hydrogenation of epoxides to generate... 

The function of Co (salpr)(OH) as a base under neutral conditions has been demonstrated in the following reactions (1) conversion of 2 -hydroxychalcones to flavanones in methanol [87], (2) retro-Claisen reaction of l-(2-hydroxyphenyl)-3-phenyl-1,3-propanediones in methanol [88], (3) the synthesis of 4ff-Chromen-4-ones from l-(2-hydroxyphenyl)-l,3-propanediones in 2,2,2-trifluoroethanol [89], (4) highly selective formation of a-Aryl-a-hydroxyacetic esters from arylglyoxals in an alcohol [90] and (5) the reaction of dibenzoylmethanes with formaldehyde to give 1,1,3,3,-tetrabenzoyl-propanes in dichloromethane [91]. 

Aroxyacoxy compds. a-Diketone monoketals Enolperoxides Glycidic acid esters a-Hydroxyacetals 1-Hydroxylactones a-Ketoacetals a-Keto-Y-lactones Lactolesters... 

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