Comparative morphology of myrmecophilous immature stages of European Microdon species (Diptera: Syrphidae): updated identification key and new diagnostic characters.

Hoverflies (Diptera: Syrphidae) of the genus Microdon Meigen have larvae that live in ant nests where they are predatory on ant larvae. Reflecting the exceptional challenges of this very specialized lifestyle, Microdon eggs, larvae and puparia are highly distinctive in their morphology. Detailed descriptions of these immature stages is, however, lacking for all but a very few species, and much of this has been limited through the sole use of light microscopes.

Unlocking Access to Enantiopure Fused Uracils by Chemodivergent [4+2] Cross-Cycloadditions: DFT-Supported Homo-Synergistic Organocatalytic Approach.

The discovery of chemical methods enabling the construction of carbocycle-fused uracils which embody a three-dimensional and functional-group-rich architecture is a useful tool in medicinal chemistry oriented synthesis. In this work, an unprecedented amine-catalyzed [4+2] cross-cycloaddition is documented; it involves remotely enolizable 6-methyluracil-5-carbaldehydes and β-aryl enals, and chemoselectively produces two novel bicyclic and tricyclic fused uracil chemotypes in good yields with a maximum level of enantiocontrol. In-depth mechanistic investigations and control experiments support an intriguing homo-synergistic organocatalytic approach, where the same amine organocatalyst concomitantly engages both aldehyde partners in a stepwise eliminative [4+2] cycloaddition, whose vinylogous iminium ion intermediate product may diverge-depending upon conditions-to either bicyclic targets by hydrolysis or tricyclic products by a second homo-synergistic trienamine-mediated stepwise [4+2] cycloaddition.

Exploiting the Distal Reactivity of Indolyl Methylenemalononitriles: An Asymmetric Organocatalyzed [4+2] Cycloaddition with Enals Enables the Assembly of Elusive Dihydrocarbazoles.

An unprecedented technique for the in situ generation of indolyl ortho-quinodimethanes from 2-methylindole-based methylenemalononitriles by amine-mediated remote C(sp(3) )-H deprotonation was developed. These intermediates were efficiently trapped by diverse enals to provide a rapid entry to 2,9-dihydro-1H-carbazole-3-carboxyaldehyde structures through a formal asymmetric [4+2] eliminative cycloaddition governed by a α,α-diphenylprolinol trimethylsilyl ether catalyst.

Organocatalytic, Asymmetric Eliminative [4+2] Cycloaddition of Allylidene Malononitriles with Enals: Rapid Entry to Cyclohexadiene-Embedding Linear and Angular Polycycles.

A direct aminocatalytic synthesis has been developed for the chemo-, regio-, diastereo-, and enantioselective construction of densely substituted polycyclic carbaldehydes containing fused cyclohexadiene rings. The chemistry utilizes, for the first time, remotely enolizable π-extended allylidenemalononitriles as electron-rich 1,3-diene precursors in a direct eliminative [4+2] cycloaddition with both aromatic and aliphatic α,β-unsaturated aldehydes. The generality of the process is demonstrated by approaching 6,6-, 5,6-, 7,6-, 6,6,6-, and 6,5,6-fused ring systems, as well as biorelevant steroid-like 6,6,6,6,5- and 6,6,6,5,6-rings.

Computational intelligence techniques for tactile sensing systems.

Tactile sensing helps robots interact with humans and objects effectively in real environments. Piezoelectric polymer sensors provide the functional building blocks of the robotic electronic skin, mainly thanks to their flexibility and suitability for detecting dynamic contact events and for recognizing the touch modality. The paper focuses on the ability of tactile sensing systems to support the challenging recognition of certain qualities/modalities of touch.

Diastereo- and enantioselective catalytic vinylogous Mukaiyama-Mannich reactions of pyrrole-based silyl dienolates with alkyl-substituted aldehydes.

A reliable, catalytic asymmetric vinylogous Mukaiyama-Mannich reaction of pyrrole-based silyl dienolates is introduced that is particularly apt for alkyl- and α-alkoxyalkyl-substituted aldehydes. The reaction course is effectively orchestrated by the Hoveyda-Snapper amino acid-based chiral ligand/silver(I) catalyst combination to produce valuable vicinal diamino carbonyl compounds in high yields, with virtually complete γ-site- and anti-selectivity and significant catalyst-to-product chirality transfer. The utility of the Mannich products can be seen in the synthesis of an unprecedented perhydrofuro[3,2-b]pyrrolone product, an aza-analogue of naturally occurring (+)-goniofufurone.

Rare-earth ion doped up-conversion materials for photovoltaic applications.

With the aim of utilizing the infrared region of solar radiation to improve solar cell performance, significant progress, including theoretical analysis and experimental achievement, has been made in the field of up-conversion for photovoltaic applications. This Research News article reviews recent progress in the development of rear-earth (RE) ion doped up-conversion materials for solar cell applications. In addition, new trends for RE-ion-doped phosphors are briefly discussed, among them trivalent RE-ion-doped up-conversion materials for organic solar cell applications.

Uncatalyzed, diastereoselective vinylogous Mukaiyama aldol reactions on aqueous media: pyrrole vs furan 2-silyloxy dienes.

The first uncatalyzed, diastereoselective vinylogous Mukaiyama aldol reaction is reported, between pyrrole/furan-based dienoxy silanes and aromatic aldehydes on salty water/methanol medium, at almost human body temperature, under ultrasonic irradiation. With pyrrole dienes the reaction is anti-selective, while that of furan dienes is syn-selective. The dual role of water as both reaction medium and promoter is highlighted.

Asymmetric total synthesis of 1-deoxy-7,8-di-epi-castanospermine.

An efficient, stereocontrolled synthesis of (6S,7S,8S,8aR)-6,7,8-trihydroxyindolizidine (alias 1-deoxy-7,8-di-epi-castanospermine) (14) has been developed, which exploits an asymmetric vinylogous Mukaiyama aldol reaction (VMAR) between N-(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyloxy)pyrrole (1) and 2,3-O-isopropylidene-D-glyceraldehyde (2) to construct the initial pyrrolidine building block 3, and an ene-ene ring closing metathesis reaction (RCM) (9 to 10) to install the indolizidine skeleton. The synthetic sequence was 13 steps, proceeding in 19.5% overall yield.

Hybrid Root SEAL (MetaSEAL) creates hybrid layers in radicular dentin only when EDTA is used as the final rinse.

Purpose: To test if the hybrid layer formation by Hybrid Root SEAL (Sun Medical Co.), a 4-META-containing auto-adhesive self-etching root canal sealer, is affected by the sequence of irrigants employed for removing canal wall smear layers during root canal treatment.

Methods: Single-rooted teeth were shaped and irrigated with EDTA as initial rinse/NaOCl as active final rinse (Group 1), or NaOCl as initial rinse/EDTA as active final rinse (Group 2).

In vitro cytotoxicity evaluation of a self-adhesive, methacrylate resin-based root canal sealer.

This study compared the cytotoxicity of MetaSEAL (Parkell Inc, Farmington, NY), a methacrylate resin-based sealer with an epoxy resin-based (AH Plus Jet; Dentsply Caulk, Milford, DE) and a zinc oxide-eugenol-based sealer (Pulp Canal Sealer; SybronEndo, Orange, CA). Five-millimeter diameter disks prepared from the respective sealer and disks prepared from Teflon (negative control) and polymethyl methacrylate (positive control) were placed in direct contact with a rat osteosarcoma (ROS) 17/2.8 rat osteoblast-like cell line at six intervals after setting completely at 72 hours and for 5 succeeding weeks after the disks were immersed in simulated body fluid.

Streamlined, asymmetric synthesis of 8,4'-oxyneolignans.

Highly direct, modular syntheses of several natural 8,4'-oxyneolignans [(-)-1, (+)-1, (-)-2, and (-)-3] and some related variants [(-)-26, (+)-26, (+)-27, and (-)-28] are reported. Utilizing (S)- or (R)-methyl lactate as the chiral sources, two complementary syn- or anti-oriented routes were designed, encompassing nine and five steps, which were carried out to deliver the targets in an enantiomerically pure form. The embodiment of the two independent aryl and aryloxy moieties onto the lactate frame was performed according to a diversity-oriented protocol from the common precursors, aldehydes 6 and ent-6 for the syn-oriented routes and mesyl esters 19 and ent-19 for the anti-oriented routes.

New enantioselective entry to cycloheptane amino acid polyols.

[reaction: see text] A diversity-oriented protocol has been developed for the assembly of densely hydroxylated cycloheptane amino acids via succession of a vinylogous Mukaiyama aldol reaction (VMAR), a Morita-Baylis-Hillman reaction (MBHR), and an intramolecular pinacol coupling reaction (IPCR). The plan utilizes D- or L-configured glyceraldehyde derivatives as "chiral" surrogates of glyoxal and N-[(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyl)oxy]pyrrole as the synthetic equivalent of the alpha,gamma-dianion of gamma-aminobutanoic acid. The parallel, asymmetric syntheses of four cycloheptane representatives proceed with high diastereocontrol and virtually complete enantioselectivity in ten steps and overall yields of 15-37%.

Variable strategy toward carbasugars and relatives. 6. Diastereoselective synthesis of 2-deoxy-2-amino-5a-carba-beta-L-mannopyranuronic acid and 2-deoxy-2-amino-5a-carba-beta-L-mannopyranose.

Efficient, total syntheses of novel 2-deoxy-2-amino-5a-carba-beta-L-mannopyranuronic acid (1) and 2-deoxy-2-amino-5a-carba-beta-L-mannopyranose (2), a positional stereoisomer of validamine, have been achieved in 28% and 24% overall yields and in 12 steps and 13 steps, respectively, from 2-[(tert-butyldimethylsilyl)oxy]furan (3) and (2S)-2,3-O-isopropylideneglyceraldehyde N-benzyl imine (4) via two highly diastereoselective Mukaiyama aldol-related chemical maneuvers. The strategy, which furnishes the targeted carbasugars in enantiopure forms, allows for complete control of the configuration at all five contiguous stereocenters of the targets by utilizing the sole element of chirality present in the aldimine progenitor 4.

Variable strategy toward carbasugars and relatives. 5.(1) Focus on preparation of chiral nonracemic medium-sized carbocycles.

The feasibility of sequential vinylogous aldol (intermolecular)/silylative aldol (intramolecular) addition reactions involving furan- and pyrrole-based dienoxysilanes, 6 and 12, in the synthesis of carbasugar frameworks is illustrated by the preparation of the scantily investigated carbaseptanose and carbaoctanose representatives of this class of compounds. The target compounds, 1, 2, 3, ent-2, ent-3, and 4, were obtained from readily available carbohydrate precursors (5 and 19) in yields of 21-30% over 8-12 steps. The irreversible silylative ring-closing aldolisation of gamma-substituted dihydro-5H-furan-2-one and pyrrolidin-2-one aldehydes (9, 16, ent-16, and 22) driven by the TBSOTf/Pr(i)(2)EtN Lewis acid-Lewis base couple was shown to be a practical, diastereoselective maneuver to forge the densely functionalized, medium-sized core carbocycles.

Variable strategy toward carbasugars and relatives. 4. Viable access to (4a-carbapentofuranosyl)amines, (5a-carbahexopyranosyl)amines, and amino acids thereof.

A chiral, divergent synthesis of two carbafuranosylamines, 1 and 2, two carbapyranosylamines, 3 and 4, two carbafuranosylamino acids, 5 and 6, and two carbapyranosylamino acids, 7 and 8, has been achieved. Highlights of the procedure include the following: a diastereoselective crossed vinylogous Mukaiyama aldol coupling between N-(tert-butoxycarbonyl)-2-[(tert-butyldimethylsilyl)oxy]pyrrole (TBSOP, 9) and 2,3-O-isopropylidene-D-glyceraldehyde (10) for the assembly of the target compound carbon backbone; a high-yielding silylative cycloaldolization that gives the cyclopentanoid and cyclohexanoid motifs; and a reductive or hydrolytic breakage of the lactam C(O)-N link to liberate the carbasugar and install the desired pseudo-anomeric amine and the hydroxymethyl or carboxyl functionalities. The sequences leading to trans-configured carbafuranosyl compounds 1 and 5 and carbapyranosyl compounds 3 and 7 were 12- and 13-step processes, with overall yields of 34%, 35%, 17%, and 16%.