Enantioselective synthesis of the pyrroloquinoline core of the martinellines

[equation--see text] The first enantioselective synthesis of the martinelline core (-)-3 is reported. The synthesis of (-)-3 from N-allyl-N-(benzyloxycarbonyl)-2-iodoaniline (12) proceeded in seven steps and 23% overall yield. In addition, the preparation of a carbocyclic model system is described.     

Solution-phase synthesis of a combinatorial library of 3-[4-(coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acid amides

The parallel solution-phase synthesis of a new combinatorial library of 3-[4-(R1-coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acid amides 9 has been developed. The synthesis involves two steps: 1) the synthesis of core building blocks - 3- [4-(coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acids, 6 - by the reaction of 3-(omega-bromacetyl)coumarins 1 with 3-amino(thioxo)methylcarbamoylpropanoic acid (5); 2) the synthesis of the corresponding 3-[4-(coumarin-3-yl)-1,3-thiazol-2-yl- carbamoyl]propanoic acids amides 9 using 1,1'-carbonyldimidazole as a coupling reagent. The advantages of the method compared to existing ones are discussed.     

Chemistry of 3-(1H-Indol-3-yl)-3-oxopropanenitrile

This review highlighted the methods used for the synthesis of different heterocyclic compounds derived from 3-(1H-indol-3-yl)-3-oxopropanenitrile. The reactivity and their synthetic importance were investigated. In this context, recent progress in the synthesis and use of 3-(1H-indol-3-yl)-3-oxopropanenitrile as precursors for heterocyclic compounds is reviewed.     

Enantioselective synthesis for the (-)-antipode of the pyrazinone marine alkaloid, hamacanthin A.

A short enantioselective total synthesis for the (-)-antipode of the antifungal marine alkaloid, hamacanthin A, (6R)-3,6-bis(6-bromoindol-3-yl)-5,6-dihydro-2(1H)-pyrazinone, is described. This synthesis proceeds through the coupling of 3-indolyl-alpha-oxoacetyl chloride and 3-indolyl azidoethylamine, followed by intramolecular aza-Wittig type cyclization. A concise and useful approach for the synthesis of (1R)-1-(indol-3-yl)-2-azidoethylamine using the Sharpless asymmetric dihydroxylation reaction followed by stereospecific azidation is also presented.     

Unprecedented oxidation of a phenylglycinol-derived 2-pyridone: enantioselective synthesis of polyhydroxypiperidines

[reaction: see text]. The phenylglycinol-derived 2-pyridone 1 undergoes m-CPBA oxidation steroselectively leading to the chiral nonracemic unsaturated bicyclic hydroxylactam 2, from which the enantioselective synthesis of (3R,5R)-3,4,5-trihydroxypiperidine (16) and the formal synthesis of the azasugar epiisofagomine are described. The enantioselective synthesis of (S)-N-Boc-3-hydroxypiperidine and (3R,4S)-3,4-dihydroxypiperidine is also reported.     

Pyrrolothienopyrazines: Synthèse de la pyrrolo[1,2-a]thieno[3,2-e]pyrazine et de la pyrrolo[1,2-a]thieno[2,3-e]pyrazine

The synthesis of pyrrolo[1,2-α]thieno[3,2-e]pyrazine and pyrrolo[1,2-α]-thieno[2,3-e]pyrazine is described. These syntheses could be achieved by intramolecular cyclization of 2- (and 3-) (1-pyrrolyl)-3- (and -2)-thienyl-amines obtained by hydrolysis of carbamates or by cleavage of the corresponding ureas. An original way giving better results was also studied via a Curtius rearrangement by reaction between the azide and aldehyde groupings. The synthesis of 2- (and -3)-2-formyl-1-pyrrolyl)-2- (and -3)-thenoylazide is described.     

Enantioselective syntheses of (+)-xylarenal A and ent-xylarenal A

[reaction: see text] The total synthesis of the sesquiterpenoid xylarenal A is reported. This first synthetic entry to an eremophilane terpenoid with an exocyclic vinyl aldehyde unit involves the use of the bicyclic enone (+)-3, which after a gamma-oxidation and alpha'-allylation leads to the formation of the ketone (+)-8. After its acylation, an oxidative cleavage of the allyl side chain followed by alpha-methylenation of the resulting aldehyde gives (+)-xylarenal A (1). The synthesis of (-)-xylarenal A from (-)-3 is also reported. Moreover, the first total synthesis of the trinoreremophilane (+)-1alpha-hydroxyisoondetianone (5) is described.     

Selective methodologies for the synthesis of biologically active piperidinic compounds

The synthesis of optically active substituted piperidines has been achieved by using four different methodologies. The first one is an intramolecular nucleophilic displacement of activated alcohol moieties that was used to build up the piperidine ring of (-)-prosophylline and (-)-slaframine, and the second one is a ring-closing metathesis of unsaturated amines which was employed in the synthesis of (+)-sedamine and 4a,5-dihydrostreptazoline. The third methodology is the alpha-functionalization of N-Boc piperidines which was particularly useful in the synthesis of argatroban, and the fourth one is a ring expansion of prolinols to 3-chloropiperidines or 3-hydroxypiperidines which was utilized to synthesize (-)-paroxetine, (-)-pseudoconhydrine, the piperidine ring of (-)-velbanamine and (+)-zamifenacin.     

Configurational studies on 2-[∝-(2-ethoxyphenoxy)benzyl] morpholine fce 20124

The relative configuration of the two diastereoisomers of (±)2-[?-(2-ethoxyphenoxy)benzyl] morpholine is determined by a synthesis involving regio and stereo specific reactions. (RS,RS) diastereoisomer FCE 20124 was separated into its (+) and (-) enantiomers both by crystallization of the optically active mandelate salt and by a multi-step synthesis from (+)-(2S,3R)-3-phenylglycidic acid.     

Facile Synthesis of 1,2-Dialkyl-3-Phenyl-4-Quinolinones

The synthesis of 1,2-dialkyl-3-phenyl-4-quinolinones (1) is readily accomplished by a low-temperature reaction of an N-alkylisatoic anhydride with the therraodynamic potassium enolate of phenyl-acetone. The reaction has also been extended to encompass the synthesis of the more complex 2-(3-hydroxy-propyl)-3-(4-fluorophenyl)-1-methyl-4(1H)-quinolinone (10).     

SuperQuat N-acyl-5,5-dimethyloxazolidin-2-ones for the asymmetric synthesis of alpha-alkyl and beta-alkyl aldehydes

The proclivity of alpha-branched N-2'-benzyl-3'-phenylpropionyl derivatives of (S)-4-benzyl-5,5-dimethyl-, (S)-4-phenyl-5,5-dimethyl-, (S)-4-isopropyl-5,5-dimethyl-, (S)-4-benzyl- and (S)-4-benzyl-5,5-diphenyl-oxazolidin-2-ones to generate directly 2-benzyl-3-phenylpropionaldehyde upon hydride reduction with DIBAL is investigated. The (S)-4-benzyl-5,5-dimethyl-derivative proved optimal for inhibition of endocyclic nucleophilic attack, giving 2-benzyl-3-phenylpropionaldehyde in good yield upon reduction. Application of this methodology for the asymmetric synthesis of chiral aldehydes via diastereoselective enolate alkylation of a range of (S)-N-acyl-4-benzyl-5,5-dimethyloxazolidin-2-ones to afford and array of alpha-substituted-N-acyl-5,5-dimethyloxazolidin- 2-ones (85-94% de) and subsequent reduction with DIBAL afforded directly non-racemic alpha-substituted aldehydes without loss of stereochemical integrity (87-94% ee). The extension of this protocol for the asymmetric synthesis of beta-substituted aldehydes is demonstrated, via the diastereoselective conjugate addition of a range of organocuprates to (S)-N-acyl-4-phenyl-5,5-dimethyloxazolidin-2-ones which proceeds with high diastereoselectivity (generally > 95% de). Reduction of the conjugate addition products with DIBAL gives non-racemic beta-substituted aldehydes in high yields and in high ee (generally > 95% ee). This methodology is exemplified by the asymmetric synthesis of (R)-3-isopropenylhept-6-enal, which has previously been used in the synthesis of (3Z,6R)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate, a component of the sex pheromones of the California red scale.     

Stereoselective photochemical 1,3-dioxolane addition to 5-alkoxymethyl-2(5H)-furanone: synthesis of bis-tetrahydrofuranyl ligand for HIV protease inhibitor UIC-94017 (TMC-114)

A convenient synthesis of (3R,3aS,6aR)-3-hydroxyhexahydrofuro[2,3-b]furan, a high-affinity nonpeptidal ligand for HIV protease inhibitor UIC-94017, is described. This inhibitor is undergoing advanced clinical trials. The synthesis utilizes a novel stereoselective photochemical 1,3-dioxolane addition to 5(S)-benzyloxymethyl-2(5H)-furanone as the key step. The requisite furanone derivative was prepared in high enantiomeric excess by an immobilized lipase-catalyzed selective acylation of (+/-)-1-(benzyloxy)-3-buten-2-ol and a ring-closing olefin metathesis with Grubbs' catalyst. Optically active bis-THF was converted to protease inhibitor 2 (UIC-94017).     

Synthesis of 5-(trifluoromethyl)cyclohexane-1,3-dione and 3-amino-5-(trifluoromethyl)cyclohex-2-en-1-one: new trifluoromethyl building block

A simple synthesis of 5-(trifluoromethyl)cyclohexane-1,3-dione and 3-amino-5-(trifluoromethyl)cyclohex-2-en-1-one from the sodium salt of methyl or ethyl-4-hydroxy-2-oxo-6-(trifluoromethyl)cyclohex-3-en-1-oate is demonstrated. The compounds represent highly functionalized reactive intermediates for the synthesis of organic and heterocyclic compounds containing a trifluoromethyl group.     

p-Menthane-3-carboxaldehyde: a useful chiral auxiliary for the synthesis of chiral quaternary carbons of high enantiomeric purity

(+)- or (-)-p-Menthane-3-carboxaldehyde is made in two easy steps from (+)- or (-)-menthone, respectively. This auxiliary allows for the synthesis of carbonyl compounds bearing a alpha-chiral quaternary carbon. The flexibility, efficiency, and ease of use of the method are demonstrated in a series of examples, which include the total synthesis of (+)-cuparenone as well as a partial synthesis of (-)-cassiol.     

Solid-phase synthesis of a type II′ β-turn peptido-mimetic library

The solid-phase synthesis of a dipeptide derived 2-amino-3-oxohexahydroindolizino[8,7-b]indole-5-carboxylate system (IBTM) is described. The IBTM moiety is formed via a solid-phase mediated Pictet-Spengler reaction of N-terminal tryptophan and the 4-{N-[1-(4,4-dimethyl-2,6-dioxocyclohexylidene)-3-methylbutyl]amino}benzyl (Dmab) ester of Fmoc protected aspartic acid β-aldehyde followed by γ-lactamization. This synthesis allows the regio- and stereoselective incorporation of a dipeptide surrogate of type II′ β-turns. The procedure is easily adaptable to combinatorial synthesis and a 576-member library was synthesized.     

Totally stereocontrolled synthesis of α,β-diamino acids by addition of Grignard reagents to nitrones derived from l-serine

The asymmetric synthesis of protected (2R,3S)- and (2R,3R)-3-substituted 2,3-α-amino acids is reported. The key step in the synthesis of these compounds is the diastereoselective addition of Grignard reagents to α-amino nitrones derived from l-serine. Total stereocontrol of the addition step is achieved by changing the protecting groups in the starting material. The predominant selectivity in each case can be reasonably interpreted in terms of steric effects of the substituents.     

Synthesis of thiazolotriazepinones

The synthesis of 4,5-dihydro-7-phenylthiazolo[2,3-c][1,2,4]triazepin-3(2H)-one ( 4 ) from 2-propenoic acid 2-(4-phenyl-2-thiazolyl)hydrazide ( 14 ), is reported. A synthesis of 4 which was reported earlier by Mahajan, Sondhi and Ralhan (9), from 3-chloropropanoic acid 2-(4-phenyl-2-thiazolyl)hydrazide ( 3 ), is erroneous. We were able to cyclize 3 to 1-(4-phenyl-2-thiazolyl)-3-pyrazolidinone ( 5 ). The cyclizations of 14 to 4 and 3 to 5 are consistent with the Baldwin Rules for Ring Closure.     

Photocatalytic cleavage of hydroxytriazenes: a solid-state synthesis of azo-dyes under sunlight irradiation

Sunlight-induced decomposition of hydroxytriazenes, and green photochemical synthesis of azo-dyes is described. Three substituted hydroxytriazenes, viz: 3-hydroxy-3-(2-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (o-CFHT), 3-hydroxy-3-(3-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (m-CFHT), and 3-hydroxy-3-(4-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (p-CFHT) were co-crystallized with ??-naphthol in equimolar ratio and exposed to sunlight for 9?C10?h. The reaction resulted in formation of azo-dyes which were identified by comparison with the products obtained by the conventional method (standard azo-dye), by use of HPLC. A probable mechanism has been suggested. This is first eco-friendly synthesis of azo-dyes using hydroxytriazenes.     

Beta-hydroxy-gamma-lactones as chiral building blocks for the enantioselective synthesis of marine natural products

The enantioselective synthesis of trans-(+)-laurediol, (2S,3S,5R)-5-[(1R)-1-hydroxy-9-decenyl]-2-pentyltetrahydro-3-furanol, and (2S,3S,5S)-5-[(1S)-1-hydroxy-9-decenyl]-2-pentyltetrahydro-3-furanol are described. In addition, a formal synthesis of trans-(-)-kumausyne is also developed. All the synthetic procedures have in common the use of enantiomerically enriched beta-hydroxy-gamma-lactones, easily available by Sharpless asymmetric dihydroxylation (AD) from the suitable beta,gamma-unsaturated ester. The use of Katsuki-Sharpless asymmetric epoxidation (AE) as an additional enantioselective reaction provides cyclic compounds of high enantiomeric purity.     

Oligofuranosides containing conformationally restricted residues: synthesis and conformational analysis

The synthesis of a panel of arabinofuranosyl oligosaccharide analogues (5-13) in which one ring is locked into either the E(3) or OE conformation is described. The E(3)-locked scaffolds 15 and 16 required for the synthesis of 5-10 were prepared in one step from known 1,5-anhydroalditols. A number of routes were explored for the preparation of the OE-locked monosaccharide derivative 17 needed for the preparation of 11-13. The successful synthesis of 17 was achieved in 17 steps from D-arabinose. Subsequent analysis of 5-13 by 1H NMR spectroscopy demonstrated that the locked residue does not exert any detectable influence upon the conformers populated by adjacent conformationally unrestricted furanose rings.