Totally selective reaction of CO2 with enantiopure amino epoxides under mild reaction conditions. synthesis and synthetic applications of enantiopure (4R,1'S)- or (4S,1'S)-4-(1-Aminoalkyl)-2-oxo-1,3-dioxolanes

The reaction of chiral (2R,1'S)- or (2S,1'S)-2-(1-aminoalkyl)epoxides 1 or 2 with CO2, generated from acidic treatment of an aqueous solution of NaHCO3 at room temperature, efficiently afforded enantiopure cyclic carbonates 3 or 4, respectively, with total selectivity. Compounds 3 and 4 were readily transformed into the corresponding diols 7 and 8 by reaction with LiAlH4 or by basic hydrolysis. When compounds 3 or 4 were allowed to react with methyllithium at -78 degrees C, O1-acetylalkane-1,2-diols 9 and 10 were obtained with total or high selectivity.     

Totally selective synthesis of enantiopure (3S,5S)- and (3R,5R)-4-amino-3,5-dihydroxypiperidines from aminodiepoxides derived from serine

The transformation of enantiopure (2R,4R)- and (2S,4S)-N,N-dibenzyl-1,2:4,5-diepoxypentan-3-amine, 1 and 2, into the corresponding enantiopure (3S,5S)- and (3R,5R)-3,5-dihydroxy-3-aminopiperidines, 3 and 4 respectively, is described. The opening of the two epoxide rings with a range of amines takes place with total regioselectivity and high yields, in the presence of LiClO4. A mechanism to explain this transformation is proposed.     

Convenient access to sterically hindered C2 chiral 2,2,5,5-tetraphenyltetrahydrofuran-3,4-diols: intramolecular selective 1,4-cyclocondensation of (2R,3R)- and (2S,3S)-1,1,4,4-tetraphenylbutanetetraols

Sterically hindered C₂ chiral (3R,4R)- and (3S,4S)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diols have been conveniently prepared in a very high yield via heterogeneous intramolecular selective 1,4-cyclocondensation of (2R,3R)- and (2S,3S)-1,1,4,4-tetraphenylbutanetetraol in concentrated hydrohalic acids, respectively. Preliminary examination of additives for the Barbas–List reaction showed that in certain cases, the hindered C₂ chiral tetrahydrofuran-3,4-diols were better chiral auxiliaries than enantiopure (R)- and (S)-1,1′-bi-2-naphthols.     

Regioselective ring opening of amino epoxides with nitriles: an easy synthesis of (2R,3S)- and (2S,3S)-1,3-diaminoalkan-2-ols with differently protected amine functions

[reaction: see text] Transformation of enantiopure (2R,1'S)- or (2S,1'S)-2-(1-aminoalkyl)epoxides 1 or 2 into the corresponding (2R,3S)- and (2S,3S)-1,3-diaminoalkan-2-ols 3 or 4 is described. The opening of the epoxide ring with different nitriles (Ritter reaction) takes place with total selectivity and in high yields in the presence of BF3.Et2O. Interestingly, the two amine groups are differently protected. A mechanism to explain this transformation is proposed.     

Synthesis and structure determination of diastereoisomeric (1R,2R,6S)-6-(3-{[(1RS)-1-(1-adamantyl)ethyl]amino}prop-1-en-2-yl)-3-methylcyclohex-3-ene-1,2-diols

Epimeric (1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol derivatives containing a rimantadine residue have been synthesized, and their steric structure has been determined using NOESY technique and DFT quantum chemical calculations.     

Synthesis of enantiopure (R,R)- and (S,S)-cis-2,3-propanoprolines

A novel approach to the synthesis of an enantiopure bicyclic proline analogue, hexahydrocyclopenta[b]pyrrole-6a(1H)-carboxylic acid (‘2,3-propanoproline’), has been developed. The method relied on tandem Strecker-nucleophilic cyclization reaction of 2-(2-bromoethyl)cyclopentanone. The overall synthetic scheme included six steps and resulted in 18% overall yield of both enantiomers of the title amino acid.     

Fractional crystallisation of (±)-iso-amarine with mandelic acid: convenient access to (R,R)- and (S,S)-1,2-diamino-1,2-diphenylethanes

(±)-iso-Amarine can be conveniently resolved via 1:1 salt formation with either hand of mandelic acid. Enantiopure iso-amarine can be acetylated and hydrolysed to give enantiopure 1,2-diamino-1,2-diphenylethanes.     

Highly selective R,S-coordination of non racemic (1R,2R)-(1,2-dialkyl)-1,2-diamine cyclohexane derivatives to palladium dichloride

In non-racemic (1R,2R)-(1,2-dialkyl)-1,2-diaminocyclohexane palladium dichloride complexes the C2 symmetry of the diamine ligand is broken, resulting in selective R,S-coordination.     

Studies towards the synthesis of (1R,2S)- and (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonates and (1S,2S)- and (1R,2S)-2,3-epoxy-1-hydroxypropylphosphonates

The trans-configured fosfomycin analogue, diethyl (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonate, was synthesised by the intramolecular Williamson reaction of diethyl (1S,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate. The cis-analogue was obtained as O-ethyl or O,O-diethyl (1R,2S)-1,2-epoxy-3-hydroxypropylphosphonates, when (1R,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate or its 3-O-trityl derivative were used as starting materials, respectively. The intramolecular Williamson cyclisations of diethyl (1S,2R)- and (1R,2S)-1-benzyloxy-3-hydroxy-2-mesyloxypropylphosphonates led to diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, respectively, with the concomitant formation of diethyl (E)-1-benzyloxy-3-hydroxyprop-1-en-1-phosphonate. From diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, enantiomerically pure diethyl (1S,2S)- and (1R,2S)-1,2-dihydroxypropylphosphonates were obtained by catalytic hydrogenation, while diethyl (1S,2S)- and (1R,2S)-3-acetamido-1,2-dihydroxypropylphosphonates were produced after epoxide ring opening with dibenzylamine, acetylation and hydrogenolysis.     

Enantioselective acylation of 1,2- and 1,3-diols catalyzed by aminophosphinite derivatives of (1S,2R)-1-amino-2-indanol

A phosphinite derivative that can be easily prepared in two steps from commercially available aminoindanol was found to be an effective catalyst for enantioselective acylation of diols. For the asymmetric desymmetrization of meso-1,2-diols, the corresponding monoester was obtained in up to 95% ee from the reaction in the presence of 5 mol % catalyst.     

Coordination compounds of copper(II) with substituted 3-{[(2-hydroxyphenyl)methylidene]amino}propane-1,2-diols

3-{[(2-Hydroxyphenyl)methylidene]amino}propane-1,2-diol, its 5-chloro-,5-bromo-, 5-nitro-, 3-methoxy derivatives, and 3-{[(2-hydroxynaphthyl-1)methylidene]amino}propane-1,2-diol react with hydrates of copper(II) chloride, bromide and nitrate in ethanol to form coordination compounds Cu(L)X·nH₂O. Template condensation reaction between 3-aminopropane-1,2-diol and 2,3-, 2,4- or 2,5-dihydroxybenzaldehyde in the presence of copper(II) nitrate trihydrate results in similar compounds Cu(L)NO₃·nH₂O. Structure of some of the condensation products was identified by X-ray analysis. Thermolysis of the substances obtained occurs through the dehydration step (70–90°C) and complete thermal decomposition (290–560°C).     

Introduction of cis-vicinal amino alcohol functionality into the cyclohexane ring employing (1S,2S)-2-amino-1,2-diphenylethanol: synthesis of enantiopure aminocyclohexitols

Pd(0)-catalyzed allylic amination of 3-bromocyclohexene with (1S,2S)-2-amino-1,2-diphenylethanol and subsequent intramolecular oxyselenenylation of the resulting allylic amine 6 followed by oxidation–elimination afforded the valuable cis-fused bicyclic olefin 10. Oxyselenenylation of cyclohexene with (1S,2S)-N-(benzyloxycarbonyl)-2-amino-1,2-diphenylethanol and subsequent oxidation–elimination gave the allylic ether 18. Intramolecular aminoselenenylation of 18 followed by oxidation–elimination provided the cis-fused bicyclic olefin 21, which is the regioisomer of 10. Further stereoselective transformation of 10 afforded enantiopure aminocyclohexitols.     

New analogues of fosfomycin—synthesis of diethyl (1R,2R)- and (1S,2R)-1,2-epoxy-3-hydroxypropylphosphonates

The trans-configured fosfomycin analogue, diethyl (1R,2R)-1,2-epoxy-3-hydroxypropylphosphonate, was synthesised via the intramolecular Williamson reaction from 3-O-protected (trityl or TBDMS) or even unprotected diethyl (1S,2R)-2,3-dihydroxy-1-mesyloxypropylphosphonate, which was obtained from the known diethyl (1S,2R)-2,3-O-cyclohexylidene-1,2,3-trihydroxypropylphosphonate. On the other hand, the cis-analogue, diethyl (1S,2R)-1,2-epoxy-3-hydroxypropylphosphonate, could only be prepared from diethyl (1R,2R)-2-hydroxy-1-mesyloxy-3-trityloxypropylphoshonate.     

Enantioselective synthesis of (2R,3R)- and (2S,3S)-2- [(3-chlorophenyl)-(2-methoxyphenoxy)methyl]morpholine

The enantioselective synthesis of the (R,R)- and (S,S)-enantiomers of 1 from commercially available 3-chlorocinnamic acid is reported. The Sharpless asymmetric epoxidation was used to establish the stereocenters in the synthesis of both enantiomers of 1.     

Asymmetric conjugate reductions with samarium diiodide: asymmetric synthesis of (2S,3R)- and (2S,3S)-[2-2H,3-2H]-leucine-(S)-phenylalanine dipeptides and (2S,3R)-[2-(2)H,3-2H]-phenylalanine methyl ester

The highly diastereoselective samarium diiodide and D(2)O-promoted conjugate reduction of homochiral (E)- and (Z)-benzylidene and isobutylidene diketopiperazines (E)-5,7 and (Z)-6,8 has been demonstrated. This methodology allows the asymmetric synthesis of methyl (2S,3R)-dideuteriophenylalanine 27 in > or = 95% de and >98% ee, and (2S,3R)- or (2S,3S)-dideuterioleucine-(S)-phenylalanine dipeptides 37 and 38 in moderate de, 66% and 74% respectively. A mechanism is proposed to account for this process.     

(2S,3S)-1,2-环氧基-3-叔丁氧酰胺基-4-苯丁烷的合成

以(S)-苯丙氨酸为原料,经氨基保护、与对硝基苯酚成酯后与硫叶立德反应制得(S)-1-氯-3-叔丁氧酰胺基-4-苯基-2-丁酮(3);3经Meerwein-Poondrf-Verley还原、环合等反应合成了HIV-1蛋白酶抑制剂的关键中单体——(2S,3S)-1,2-环氧基-3-叔丁氧酰胺基-4-苯丁烷,总收率约45%,其结构经1H NMR和MS确证。     

Lipase-catalyzed transesterification of 2-hydroxy-2-(pentafluorophenyl)acetonitrile leading to (1R,2R)- and (1S,2S)-bis(pentafluorophenyl)ethane-1,2-diol

Optically pure (1R,2R)- and (1S,2S)-1,2-bis(pentafluorophenyl)ethane-1,2-diol (1) were synthesized from key intermediates (R)- and (S)-2-hydroxy-2-(pentafluorophenyl)acetonitrile (2), both of which were prepared by the lipase LIP-catalyzed transesterification (E = 465). The absolute configuration of (S)-2 was determined by X-ray structural analysis after transformation into (S)-alpha-cyano-2,3,4,5,6-pentafluorobenzyl (S)-6-methoxy-alpha-methyl-2-naphthaleneacetate (S,S)-9. In addition, the crystal structure of (S,S)-9 has an interesting well-ordered packing pattern which shows face-to-face stacking interactions and end-to-end parallel contacts between the pentafluorophenyl and 6-methoxynaphthyl groups of the adjacent molecules.     

Crystallization of chiral compounds 3. 3-phenoxypropane-1,2-diol and 3-(2-halophenoxy)propane-1,2-diols

Specific features of melting of crystalline samples of 3-(2-R-phenoxy)propane-1,2-diols with different enantiomeric compositions were studied by differential scanning calorimetry. The melting points and enthalpies of melting for the racemate and individual stereoisomers were determined. Binary phase diagrams were constructed. The entropy of mixing of individual enantiomers in the liquid phase and the free energy of formation of the racemic compound were calculated. The thermochemical data indicate that the racemates are formed upon the crystallization of phenoxy-and 2-fluorophenoxy-containing compounds, while crystallization of the chloro-, bromo-, and iodo-substituted analogs would form racemic conglomerates. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 225—232, February, 2006.