Richard E. Ehrenkaufer

A general procedure for mild and rapid reduction of aliphatic and aromatic nitro compounds using ammonium formate as a catalytic hydrogen transfer agent

Abstract Various aliphatic and aromatic nitro compounds were selectively and rapidly reduced to their corresponding amino derivatives in very good yield using anhydrous ammonium formate as a catalytic hydrogen transfer agent.

A gas-solid-phase microchemical method for the synthesis of acetyl hypofluorite

Abstract The useful electrophilic fluorinating agent, acetyl hypofluorite, was obtained by passing F2 diluted in N2 through columns containing complexes of alkali metal acetates with acetic acid. Acetyl hypofluorite obtained from KOAc(HOAc)1.5 and 0.14% F2 in N2 was reacted with tri- O -acetyl-D-glucal in CCl3F to obtain tetra- O -acetyl-2-deoxy-2-fluoro-D-glucose in 68% yield based on F2. These conditions are appropriate to the radiosynthesis of 18F-labeled 2-deoxy-2-fluoro-D-glucose for positron emission tomography. Important variables were the metal cation used, the ratio of HOAc to MOAc and the water content of the complex.

Quantitative in vivo receptor binding. I: Theory and application to the muscarinic cholinergic receptor

A novel approach to in vivo receptor binding experiments is presented which allows direct quantitation of binding site densities. The method is based on an equilibrium model of tracer uptake and is designed to produce a static distribution proportional to receptor density and to minimize possible confounding influences of regional blood flow, blood- brain barrier permeability, and nonspecific binding. This technique was applied to the measurement of regional muscarinic cholinergic receptor densities in rat brain using [3H]scopolamine. Specific in vivo binding of scopolamine demonstrated saturability, a pharmacologic profile, and regional densities which are consistent with interaction of the tracer with the muscarinic receptor. Estimates of receptor density obtained with the in vivo method and in vitro measurements in homogenates were highly correlated. Furthermore, reduction in striatal muscarinic receptors following ibotenic acid lesions resulted in a significant decrease in tracer uptake in vivo, indicating that the correlation between scopolamine distribution and receptor density may be used to demonstrate pathologic conditions. We propose that the general method presented here is directly applicable to investigation of high affinity binding sites for a variety of radioligands.

A Preparative Gas-Solid-Phase Synthesis of Acetyl Hypofluorite

Abstract A simple gas-solid-phase synthesis of acetyl hypofluorite is described in which dilute fluorine in air or nitrogen is reacted with a solid complex of potassium acetate with acetic acid.

Synthesis of (18F)Perchloryl Fluoride and its Reactions with Functionalized Aryl Lithiums

Abstract [ 18 F]Perchloryl fluoride ( 18 FClO 3 ) has been synthesized by the reaction of [ 18 F]F 2 with KClO 3 and its synthetic utility demonstrated by the successful syntheses of [ 18 F] labeled 2-fluoroaniline, 2-fluoroanisole, 2-fluorobenzaldehyde and 3-fluoroveratrole by reaction with their respective ortho-lithiated aromatic precursors in 24, 34, 3 and 21% yields, respectively.

RAPID REDUCTIVE-CARBOXYLATION OF SECONDARY AMINES. ONE POT SYNTHESIS OF TERTIARY N-METHYLATED AMINES

Various tertiary N-methylated amines were synthesized by using a new reductive-carboxylation approach. Secondary amines, on carboxylation with carbon dioxide under moderate reaction conditions, afforded their corresponding carbamate esters, which, on in situ lithium aluminum hydride reduction, gave desired tertiary N-methylated amines in high yield.

ω-Difluoroamino carboxylic acids: Readily accessible fluorine-labeled fatty acid analogs

Abstract 15-Difluoroamino-pentadecanoic acid and 12-difluoroamino-dodecanoic acid were prepared by treating the corresponding lactams with F2 in aqueous acetonitrile. The intermediate N-fluorolactams were also isolated. Whereas isolated −CH2F groups introduce considerable polarity into aliphatic chains, −CH2NF2 groups did not. The −NF2 group thus appears to be a suitable isostere of the −CH3 group, where introduction of a 18F label is required for positron-based or 19F NMR imaging.