Epicardial development in the rat: a new perspective.

Development of the epicardium is critical to proper heart formation. It provides all of the precursor cells that form the coronary system and supplies signals that stimulate cardiac myocyte proliferation. The epicardium forms from mesothelial cells associated with the septum transversum and is referred to as the proepicardium (PE). Two different methods by which these PE cells colonize the developing heart have been described. In avians, PE cells form a bridge to the heart over which PE cells migrate onto the heart. In fish and mammals, PE cells form vesicles of cells that detach from the mesothelium, float through the pericardial cavity, and attach to the heart. A previous study of rat PE development investigated this process at the histological level. Protein markers have been developed since this study. Thus, we investigated this important developmental process coupled with these new markers using other visualization techniques such as scanning electron microscopy (SEM) and confocal microscopy. Finally, a novel, three-dimensional (3-D) culture system was used to confirm the identity of the PE cells. In this study, we found convincing evidence that the rat PE cells directly attach to the heart in a manner similar to that observed in avians.     

Superoxide radical anion adduct of 5,5-dimethyl-1-pyrroline N-oxide (DMPO). 2. The thermodynamics of decay and EPR spectral properties

The formation of the superoxide radical anion (O2*-) adduct of the nitrone 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as detected by electron paramagnetic resonance (EPR) spectroscopy is one of the most common techniques for O2*- detection in chemical and biological systems. However, the nature of DMPO-O2H has confounded spin-trapping investigators over the years, since there has been no independently synthesized DMPO-O2H to date. A density functional theory (DFT) approach was used to predict the isotropic hyperfine coupling constants arising from the N, beta-H, and gamma-H nuclei of DMPO-O2H using explicit interactions with water molecules as well as via a bulk dielectric effect employing the polarizable continuum model (PCM). Theoretical calculation on the thermodynamics of DMPO-O2H decay shows favorable intramolecular rearrangement to form a nitrosoaldehyde and a hydroxyl radical as products, consistent with experimental observations. Some pathways for the bimolecular decomposition of DMPO-O2H and DMPO-OH have also been computed.     

Tris(arylmethyl) derivatives of 1,3,5-trimethoxy- and 1,3,5-triethylbenzene

The hexasubstituted benzenes 7 and 9b were synthesized starting from 3 and 8b, respectively. In the crystal, 9b adopts the fully alternated conformation with all arylmethyl groups oriented syn.     

Three new flavonol malonylrhamnosides from Ribes alpinum.

Three new flavonol malonylrhamnosides, 3-O-(4"-O-malonyl)-alpha-L-rhamnopyranosides of mearnsetin, myricetin and quercetin respectively, together with the corresponding mearnsitrin, myricitrin, quercitrin and the 4-O-methyl phloracetophenone 2-O-beta-D-glucopyranoside, were isolated from the leaves of Ribes alpinum and fully characterized by spectrocopic methods including 2D NMR.     

Are α-alkoxyalkyl complexes special? 13CH coupling constant evidence.

Comlexes of type L_nMCH₂O₂CCMe₃ exhibit relatively large values of ¹J_CH for the α-carbon; however, unexpectedly large values are also found for the methyl analogs, L_nMCH₃. Thus technique does not provide evidence for any unusual interactions in the former. Cleavage of the ester linkage by MeLi proceeded cleanly only for L_nM = CpMo(Co)₃, leading to CpMo(CO)₃^?; with L_nM = Mn(CO)₅ or CpFe(CO)₂ electron transfer processes predominate. Such reactions are also observed for simple metal alkyls such as CpFe(CO)₂CH₃.     

The synthesis of the drugstore beetle pheromone (Stegobinone)

2,3-Dihydro-2,3,5-trimethyl-6-(1-methyl-2-oxobutyl)-4H-pyran-4-one ($\text{1}$ (Stegobinone), the sex pheromone of the drugstore beetle, was successfully prepared from 4,6-dimethyl-3,5,7-nonatrione ($\text{2}$) by a biogenetically plausible scheme.     

Progression of Organic Reactions on Resin Supports Monitored by Single Bead FTIR Microspectroscopy

We report the time courses of five solid-phase reactions obtained using single bead FTIR microspectroscopy. This time-resolved information aided in the determination of the required reaction time, the nature of the solid-phase reaction, and resin property, effectively assisting in the initial phase of our combinatorial chemistry efforts. Our results showed that solid-phase organic reactions proceed faster than generally speculated. In addition, we have shown that reactions on the surface and in the interior of the bead occur at the same rate for reactions studied. The reaction on the TentaGel resin was shown to be not faster than reactions on Wang resin, suggesting that the diffusion of the substrate into polystyrene bead copolymerized with 1% divinylbenzene is not rate-limiting. Finally, the capability of obtaining IR spectra from the partial surface of a single bead demonstrated the femtomolar detection limit of single bead FTIR microspectroscopy.     

Synthesis and evaluation of duocarmycin and CC-1065 analogues incorporating the 1,2,9,9a-tetrahydrocyclopropa[c]benz[e]-3-azaindol-4-one (CBA) alkylation subunit

An efficient eight-step synthesis (53% overall) and the evaluation of 1,2,9,9a-tetrahydrocyclopropa[c]benz[e]-3-azaindol-4-one (CBA) and its derivatives containing an aza variant of the CC-1065/duocarmycin alkylation subunit are detailed. This unique deep-seated aza modification provided an unprecedented 2-aza-4,4-spirocyclopropacyclohexadienone that was characterized chemically and structurally (X-ray). CBA proved structurally identical with CBI, the carbon analogue, including the stereoelectronic alignment of the key cyclopropane, its bond lengths, and the bond length of the diagnostic C3a-N2 bond, reflecting the extent of vinylogous amide (amidine) conjugation. Despite these structural similarities, CBA and its derivatives were found to be much more reactive toward solvolysis and hydrolysis, much less effective DNA alkylating agents (1000-fold), and biologically much less potent (100- to 1000-fold) than the corresponding CBI derivatives.     

A general,highly stereoselective synthesis of amines

The stereochemical course of cycloalkanone imine reductions by a variety of boron hydride reagents is described; very high stereoselectivity with substituted alkali metal borohydrides is reported.