Lesiones traqueales focales. A propósito de un caso / No disponible

Presentamos un caso de carcinoma adenoide quístico de tráquea demostrado mediante TC multidetector de 64 coronas, PET-TC, y correlación anatomopatológica, en un paciente con hemoptisis. En este artículo revisamos el diagnóstico diferencial de las lesiones traqueales únicas focales mediante tomografía computarizada (TC). Las técnicas de imagen permitieron el diagnóstico e infravaloraron la invasión de la pared traqueal en este caso, confi rmada con posterioridad mediante el estudio histológico

We present a case of adenoid cystic tracheal carcinoma detected by computerized tomography (64-MDCT) with cyto-histological correlation in a patient with hemoptysis. In this article we review the differential diagnosis of solitary focal tracheal lesions as they appear in computerized tomography (CT). In this case, image methods suggested the diagnosis but underestimated the tracheal wall invasion, which was established by histologycal examination of the resected tumor

[Solitary focal tracheal lesions. A case report]. / Lesiones traqueales focales. A propósito de un caso.

We present a case of adenoid cystic tracheal carcinoma detected by computerized tomography (64-MDCT) with cyto-histological correlation in a patient with hemoptysis. In this article we review the differential diagnosis of solitary focal tracheal lesions as they appear in computerized tomography (CT). In this case, image methods suggested the diagnosis but underestimated the tracheal wall invasion, which was established by histologycal examination of the resected tumor.

A novel use of Grubbs' carbene. Application to the catalytic deprotection of tertiary allylamines.

[reaction--see text] The first examples accounting for the catalytic deprotection of allylic amines by using reagents different from palladium catalysts have been achieved via Grubbs' carbene-mediated reaction. The current mechanistic hypothesis invokes a nitrogen-assisted ruthenium-catalyzed isomerization, followed by hydrolysis of the enamine intermediate. We believe that an unprecedented mode of ring opening of the ruthenacyclobutane was involved.

Metal-promoted allylation, propargylation, or allenylation of azetidine-2,3-diones in aqueous and anhydrous media. Application to the asymmetric synthesis of densely functionalized 3-substituted 3-hydroxy-beta-lactams.

Metal-mediated carbonyl allylation, allenylation, and propargylation of optically pure azetidine-2,3-diones were investigated in both anhydrous and aqueous environments. Different metals promoters showed varied regioselectivities on product formation during allenylation/propargylation reactions of the keto-beta-lactams. The stereochemistry of the new C3-substituted C3-hydroxy quaternary center was controlled by placing a chiral auxiliary at C4. In this way, the coupling of azetidine-2,3-diones with a variety of propenyl-, propynyl-, and allenylmetal reagents offers a convenient asymmetric entry to potentially bioactive 3-substituted 3-hydroxy-beta-lactams.

Rapid and stereocontrolled synthesis of racemic and optically pure highly functionalized pyrrolizidine systems via rearrangement of 1,3-dipolar cycloadducts derived from 2-azetidinone-tethered azomethine ylides.

This work describes a convenient procedure for the straightforward preparation of polyfunctionalized enantiopure pyrrolizidine systems. The methodology capitalizes on a HCl(g)-promoted reaction of the 1,3-dipolar cycloadducts derived from 2-azetidinone-tethered azomethine ylides, smoothly affording different types of highly functionalized bi- and tricyclic systems in racemic and optically pure forms. This process involves a selective bond cleavage of the four-membered ring, followed by a rearrangement under the reaction conditions. The synthetic route employed was shown to be compatible with a variety of 4-oxoazetidine-2-carbaldehydes, alpha-amino esters, or dipolarophiles, offering a versatile entry to pyrrolizidine systems.

Straightforward asymmetric entry to highly functionalized medium-sized rings fused to beta-lactams via chemo- and stereocontrolled divergent radical cyclization of Baylis-Hillman adducts derived from 4-oxoazetidine-2-carbaldehydes.

DABCO promoted reactions of various activated vinyl systems with optically pure 4-oxoazetidine-2-carbaldehydes 1 gave rise to Baylis-Hillman adducts 3 with excellent syn stereoselectivities, without detectable racemization. Products 3 are used for the asymmetric preparation of unusual 2-azetidinones fused to medium-sized rings via chemo- and stereocontrolled divergent radical cyclization. The formation of bicyclic beta-lactams 4-6 could be rationalized through a tandem radical Michael addition/endo cyclization or a tandem radical addition/Michael addition, depending on the electronic nature of the radical promoter.

Rapid entry to enantiopure carbacepham derivatives via Lewis acid promoted carbonyl-ene cyclization of 2-azetidinone-tethered alkenylaldehydes.

Lewis acid promoted types I and II carbonyl-ene cyclizations of 2-azetidinone-tethered alkenylaldehydes are used for the rapid, highly diastereoselective synthesis of polyfunctionalized, enantiomerically pure carbacepham derivatives. [reaction: see text]

Stereoselective allylation of 4-oxoazetidine-2-carbaldehydes. Application To the stereocontrolled synthesis of fused tricyclic beta-lactams via intramolecular diels-alder reaction of 2-azetidinone-tethered trienes

Allylation reactions of racemic and optically pure 4-oxoazetidine-2-carbaldehydes were investigated both under anhydrous conditions and in aqueous media. Different Lewis acid or metal mediators showed varied diastereoselectivities on product formation during allylation reactions of the above aldehydes with allyltrimethylsilane, allyltributylstannane, or allyl bromide. Under standard reaction conditions, tin(IV) chloride-promoted addition of allyltrimethylsilane to 4-oxoazetidine-2-carbaldehydes provided the highest diastereoselectivity and the best yield. Boron trifluoride-diethyl ether-promoted reaction of allyltributylstannane provided slightly lower diastereoselectivity with the same facial preference. Indium-promoted allylation showed a reverse diastereofacial preference, although the observed selectivity is not synthetically useful. The mesylates of these homoallylic alcohols were used for the stereoselective preparation of cis-4-butadienyl-2-azetidinones. Interestingly, mesylates having an extra alkene or alkyne tether at position 1 or 3 of the beta-lactam ring, on heating in a sealed tube with equimolecular amounts of DBU in toluene, yielded fused tricyclic 2-azetidinones through a tandem one-pot elimination-intramolecular Diels-Alder reaction.

Base-promoted isomerization of cis-4-formyl-2-azetidinones: chemoselective C4-epimerization vs rearrangement to cyclic enaminones.

Two simple, efficient, and complementary methods for the regiospecific C4-epimerization of cis-4-formyl-2-azetidinones 1-3 are described. The first method uses 40% aqueous dimethylamine as reagent in heterogeneous medium with benzene at room temperature, in the presence of benzyltributylammonium bromide (3-4 mol%) as the phase-transfer catalyst. This transformation tolerates alkyl, alkenyl, alkynyl, aryl, and alkoxy substituents at the C3 of the 2-azetidinone ring. However, limitations of this isomerization are as follows: (i) only N-(p-methoxyphenyl)-beta-lactams can be used, and (ii) transformation is less compatible with heteroatomic substituents bonded to the C3 position of the 2-azetidinone ring. A highly general solution to these problems relies on the use of sodium carbonate as the isomerization reagent in different solvents. We also describe a novel base-promoted rearrangement of the beta-lactam ring to cyclic enaminones 6 and 21, involving an E1cB-elimination reaction in cis-4-formyl-2-azetidinones.

Regio- and stereocontrolled metal-mediated carbonyl propargylation or allenylation of enantiomerically pure azetidine-2,3-diones: synthesis of highly functionalized 3-substituted 3-hydroxy-beta-lactams

Regio- and stereocontrolled metal-mediated Barbier-type reactions of azetidine-2,3-diones with differently substituted propargyl bromides offer an efficient asymmetric entry to densely functionalized 3-propargyl- (or allenyl-) substituted 3-hydroxy-beta-lactams.