Amino alcohols vicinal

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],... 

Cross-coupling reactions of nitrones with aldehydes and ketones make it possible to synthesize vicinal amino alcohols, which are common in natural products. These transformations have been performed by a new method of reduction... 

Chiral (3-amino alcohols are important building blocks for the preparation of chiral auxiliaries, ligands, and natural products (for reviews on the asymmetric synthesis and use of vicinal amino alcohols, see [44-47]). Catalytic enantioselective... 

The chiral, nonracemic bicyclic lactams, used as starting materials for stereoselective alkylation reactions, are usually prepared by treating a mixture of the enantiomerically pure vicinal amino alcohol 1 with a 3-acylpropanoic or 4-acylbutanoic acid 2 (R4 = H) under acid catalysis in toluene with azeotropic removal of the resulting water1-17. When formation of the bicyclic aminal is complete, it is isolated as a diastereomeric mixture which is usually easy to purify and provides the major diastereomer 3. An alternative method for preparation of the bicyclic lactam uses the same conditions with a 2-substituted acid (R4 =1= H). This leads to a roughly 50 50 mixture of diastereomers 3 and 4 which can be used directly for the next step2,5,12. 

The vicinal amino alcohols (S)-2-amino-3-methylbutanol [( -valinol, 1], (15, 2R)-2-amino-l-phenylpropanol [(1, 2S)-norcphcdrine, 4] and, to a lesser extent, the enantiomers of p-aminobenzenepropanol (phenylalanol, 7) have been most often used as starting materials for the preparation2-4-24,64 of enantiomerically pure 2-oxazolidinones (2,5 and 8, respectively, see... 

DIASTEREOSELECTIVE SYNTHESIS OF PROTECTED VICINAL AMINO ALCOHOLS (S)-2-[(4S)-N-tert-BUTOXYCARBONYL-2,2-DIMETHYL-1,3-... 

Nitrogen-transfer reactions of osmium imido species lead to cis diamines or amino alcohols. Reaction of 0s02(N-/-C4H9)2 [63174-13-0] with olefins produces vicinal diamines after reductive cleavage. Catalytic oxyamination of olefins using chloramine-T or AJ-chlor-AJ-argenocarbamates yields vicinal hydroxy toluenesulfonamides (112) or carbamates (113), respectively, which maybe deprotected to vicinal amino alcohols. 

In the asymmetric aminohydroxylation (AA) an olefin is converted into a vicinal amino alcohol by means of an osmium(VIII)-mediated suprafacial addition of a nitrogen and an oxygen atom to the double bond. Like the AD, the AA has been developed by modifying an originally stoichiometric, achiral version. Although the first aminohydroxylations were reported in 1976 [70], the asymmetric catalytic protocol is still underdevelopment [71]. 

Fig. 14.21. Ring expansion of cyclic ketones via the Tiffe-neau-Demjanov rearrangement. The first step consists of the additions of HCN or nitromethane, respectively, to form either the cyanohydrin or the /J-nitroalcohol, respectively. The vicinal amino alcohol A is formed in the next step by reduction with LiAlH4. TheTiffeneau-Demjanov rearrangement starts after diazota-tion with the dediazotation.

Other types of allylic amination reactions include a variety of indirect approaches such as reduction of a,P-unsaturated imines and oximes, rearrangement of aziridines, and elimination of water from vicinal amino alcohols. However, these reactions will not be considered in this chapter [2]. 

One straightforward route to the aziridine ring system is available through the ring closure of vicinal amino alcohols, an approach which has been used to prepare vinyl N-H aziridines. Thus, 4-amino-l-phenylhex-5-en-3-ol (111) was treated with sulfuryl chloride to provide the sulfamidate 112, which underwent clean thermolysis at 70 °C to form the vinyl aziridine 113 in 97% overall yield <02T5979>. 

The complexes will effect oxyamination reaction with alkenes in a stereospecific reaction (Scheme 8).290 After reductive cleavage of the intermediate alkanolaminato complex (I) (see below) vicinal amino alcohols (II) are formed. The reaction is unusual in that the new C—N bond is always formed at the least substituted terminal alkenic carbon atom, and there is a clear preference for the imido complex to use its NR group for coordination to the osmium despite the steric restraints of R.299,300 However, the least sterically hindered part of the alkene moiety is attached to. the nitrogen atom.290,291,300 The yields of amino alcohols in the reaction can be improved by addition of tertiary alkyl bulkhead amines (see below). 

Weaker method in which vicinal amino alcohols are first converted into 2-aminoethyl hydrogen sulfate esters the latter are then treated with base leading to corresponding aziridine derivative. 

Ethanolamine ammonia lyase. EAL converts ethanol-amine to acetaldehyde, with loss of ammonia. EAL depends upon adenosylcobamides, such as coenzyme B12 (3), but a range of other adenosylcobamides are also accepted as cofactors, while cobalamins with /3-ligands other than the 5 -deoxy-5 -adenosyl group (of AdoCbl) are inhibitors. Active EAL is multimeric and has an apparent molecular mass of about 560 600kDa. Similar to the mechanism of DD, a radical mechanism is proposed for the isomerization of the vicinal amino-alcohol substrates (ethanolamine, (/f)- and (5)-aminopropanol) by EAL, starting with the abstraction of an H atom from the C-1 position of the substrates. 

When amidals obtained from secondary allylic alcohols are cyclized with mercury(ll) acetate or mercury(II) acetate and trifluoroacetic acid, the corresponding 4,5-disubstituted oxazoli-dines 12 and 13 are formed. The 1,3-asymmetric induction overrides the competing 1,2-asymmet-ric induction of the allylic substituent. When the tram-isomers 12 were formed, only one diastereomer was obtained. However, when steric interactions between the substituents are low, m-diastereomers were predominantly obtained, e.g., 13, although the amount of the nans-diastereomcrs increases on increasing the bulkiness of the allylic substituent. As the oxazolid-ines obtained by mercury-induced cyclization of the amidals are easily cleaved to amino alcohols with hydrazine, this approach allows either a syn- or [Pg.849]

Preparative Methods conversion of (IR)-camphor into vicinal amino alcohol, followed by A -methylation using either aqueous formaldehyde and formic acid or methyl iodide. Purification bulb-to-bulb distillation, column chromatography. ... 

A number of atypical reactions of enamines have been developed. For example, hydroboration-oxida-tion affords stereochemically defined, vicinal amino alcohols (equation 26). Similarly, enamines have been shown to undergo reaction with diazomethane to form substituted cyclopropanes. These materials can be further transformed to a alkylated ketones by thermolysis followed by hydrolysis (equation 27). ... 

Sharpless asymmetric aminohydroxylation One-pot enantioselective synthesis of protected vicinal amino alcohols from simple alkenes. 404... 

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