The synthesis and conformational analysis of amino acid-tetrahydroanthranilic acid hybrids

The optimization of a palladium-catalyzed amidation reaction providing a new class of amino acid-tetrahydroanthranilic acid derivatives has been achieved. The scope of the reaction and preliminary conformational analysis of the resulting series of molecules is discussed.     

Some additional properties of elementary landscapes

In this work, we derive a general class of multistep composite elementary landscapes and present the first non-trivial lower (upper) bounds on local minima (maxima) associated with elementary landscapes.     

Magnetic resonance imaging of pediatric spinal dysraphism

Thirty pediatric patients with spinal dysraphism were studied with magnetic resonance imaging. A variety of dysraphic anomalies were visualized, including syringohydromyelia, tethered cord, widened spinal canal, meningomyelocele, lipomyelomeningocele, lipomeningocele, intraspinal lipoma, congenital dermal sinus tract, and scoliosis. In 29 of 30 cases, MRI diagnostically visualized spinal cord and dysraphic anatomy. A combination of T1-weighted sagittal and axial imaging planes provided the most complete visualization. In specific cases, T2-weighted examinations were useful in demonstrating likely regions of inflammation bordering infected sinus tracts. MRI demonstrates a wide variety of dysraphic spinal anomalies and effectively screens children for occult spinal dysraphism.     

MRI of the skull

Thirty-four patients with a wide variety of benign and malignant incidental skull findings on routine magnetic resonance (MR) imaging of the brain were reviewed. In most instances detection of the lesions was not difficult. However, recognition of various patterns of skull involvement in different disease processes is important. This is particularly true in differentiating benign from malignant lesions, which may be a critical factor in patient management.     

2,5,-Dimethoxy- and 2,5-di-n-butoxy-1,4-benzoquinone reactions and polymerization with 1,6-hexanediamine

The serendipitous formation of 2,5-dimethoxy- 1,4-benzoquinone is reported from the reaction of 1,4-benzoquinone with methanol, DABCO, and paraformaldehyde. This monomer, and its di-n-butoxy analog, are also available from 2,5-dihydroxy-1,4-benzoquinone. These materials are capable of novel polycondensation reactions with diamines such as 1,6-hex-anediamine. Use of m-crexsol as polymerization solvent gave a dark, insoluble product while various amide solvents lead to orange or pink polymers that had average degrees of polymerization from 5 up to >30. These polymers, Plus model compounds obtained from 1-aminopropane and N,N'- dimethyl-1,6-hexanediamine, were characterized by FTIR, solution, and solid-state NMR.     

Cardiac calcifications: difficult MRI diagnosis

Magnetic resonance imaging (MRI) and computed tomography (CT) were performed in 40 patients with a variety of cardiovascular diseases. These imaging modalities were compared to investigate their relative value in the assessment of cardiovascular diseases. Of these 40 patients, 7 were found by CT to have detectable cardiovascular calcifications. These patients included one calcified mitral stenosis, one calcified coronary artery, one calcified type B aortic dissection, two calcified myocardial infarctions, and two patients with calcific pericarditis. In several cases, MRI was misleading because of difficulty in detecting calcifications. We present a series of cases illustrating a limitation of MRI in identifying diagnostically and clinically important cardiovascular calcifications.     

Alpha-heteroarylation of esters, lactones, amides, and lactams by nucleophilic aromatic substitution

[reaction: see text] A mild and efficient alpha-heteroarylation of simple esters and amides was developed via nucleophilic aromatic substitution. The choice of NaHMDS in toluene gave the best results. A tandem alpha-heteroarylation and hydroxylation protocol using air as the oxidant afforded tertiary alcohols in good yields.