Amino alcohols Lithium aluminum hydride-Sodium

Amino alcohols Cyanotrimethylsilane, 87 Lithium aluminum hydride-Sodium... 

The reduction of a-hydroxynitriles to yield vicinal amino alcohols is conveniently accomplished with complex metal hydrides for example, lithium aluminum hydride or sodium borohydride [69]. However, it is still worth noting that a two-step chemo-enzymatic synthesis of (R)-2-amino-l-(2-furyl)ethanol for laboratory production was developed followed by successful up-scaling to kilogram scale using NaBH4/CF3COOH as reductant [70],... 

Diclofenac Diclofenac, 2-[(2,6-dichlorophenyl)-amino]-phenylacetic acid (3.2.42), is synthesized from 2-chIorobenzoic acid and 2,6-dichloroaniline. The reaction of these in the presence of sodium hydroxide and copper gives iV-(2,6-dichlorophenyl)anthranyIic acid (3.2.38), the carboxylic group of which undergoes reduction by lithium aluminum hydride. The resulting 2-[(2,6-dicholorphenyl)-amino]-benzyl alcohol (3.2.39) undergoes further chlorination by thionyl chloride into 2-[(2,6-dichlorophenyl)-amino]-ben-zylchloride (3.2.40) and further, upon reaction with sodium cyanide converts into... 

Conversion of the keto ketoxime 1 to the exo-exo-amino alcohol 2 has been accomplished by hydrogenation over Adams catalyst and by reduction with lithium aluminum hydride. Amino alcohol 2 has also been prepared from 1 by a two-stage process in which selective reduction of the ketone is carried out with sodium borohydride, and the resultant hydroxy oxime is reduced with lithium aluminum hydride or by hydrogenation over Adams catalyst. ... 

An efficient synthesis of ( )-quebrachamine is based on the construction of a suitable precursor via ring cleavage of an a-diketone monothioketal (810) (80JCS(P1)457). This monothioketal, available from 4-ethoxycarbonylcyclohexanone ethylene ketal, was fragmented to the dithianyl half ester (811) with sodium hydride in the presence of water. Reaction of (811) with tryptamine and DCC provided an amide which was converted to the stereoisomeric lactams (812) on hydrolysis of the dithiane function. Reduction of either the a- or /3-ethyl isomer with lithium aluminum hydride followed by conversion of the derived amino alcohol to its mesylate produced the amorphous quaternary salt (813). On reduction with sodium in liquid ammonia, the isomeric salts provided ( )-quebrachamine (814 Scheme 190). 

Certain aryl-substituted a- and /S-amino Intones have been successfully reduced to amino alcohols by catalytic hydrogenation over palladium, platinum, or nickel catalysts. Cleavage of the carbon chain sometimes occurs during catalytic hydrogenation of /S-amino ketones. Fair yields of the amino alcohols ate obtained in these cases by reduction with sodium amalgam in dilute acid or aluminum amalgam and water. /S-Amino aldehydes from the Mannich reaction (method 444) are reduced in excellent yields to amino alcohols by lithium aluminum hydride or by catalytic hydrogenation over Raney nickel. Lithium aluminum hydride reduces diazo ketones to 1-amino-2-alkanols (93-99%)- ... 

Amino acids are fundamental biological chemicals and most are commercially available. Exceptions and the preparation of derivatives are discussed in Section 2.4. The compounds themselves, as well as their esters, may be reduced with complex hydrides (e.g., lithium aluminum hydride or sodium borohydride) to the corresponding a-amino alcohols (mostly named after the amino acid, e.g., alaninol from alanine). As a typical example of the in situ preparation of an amino acid ester and reduction to the amino alcohol, the synthesis of (- )-(S )-phenylalaninol is given1. 

Reduction of the ketolactam 390 (having the newly assigned A/B trans stereochemistry) with sodium borohydride followed by reduction of the amide with lithium aluminum hydride gave an amino alcohol. Oxidation of this amino alcohol with chromic acid followed by rereduction with lithium aluminum hydride gave an amino alcohol different from that obtained previously. In the oxidation to the ketone 373, therefore, epimerization at C-9a must have occurred, and the two amine alcohols must have the configurations 391 and 392. Since in both compounds Bohlmann bonds were observed in the IR spectrum, the A/ ring juncture is trans. 

The 14,15-double bond present in tabersonine was introduced into the /3-ethyl isomer of lactam 491 by treatment with LDA-diphenyl disulfide followed by oxidation and elimination to give the a,fl-unsaturated lactam 492. Murphy s law operated at this point, for upon lithium aluminum hydride reduction, 492 gave only a 5% yield of the amino alcohol 493. An alternative procedure was therefore developed. Hydrolysis gave a carboxylic acid, and treatment with ethyl chloroformate and triethylamine followed by sodium borohydride in aqueous THF gave a lactam alcohol 494, which after silylation was reduced with lithium aluminum hydride to amino alcohol 493 in 58% overall yield from 492. Mesylation and elimination of HC1 in refluxing chloroform gave the unsaturated mesylate salt 482. The same salt was prepared previously by Ziegler and Bennett... 

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