Larry Weiler

Band structure parameters for solid TTFTCNQ

Abstract Molecular orbitals for the highest occupied states of TTF + and TCNQ − , calculated by the Extended Huckel Method of Hoffman, are used to compute band parameters within the tight-binding approximation for the conduction band of solid TTFTCNQ. Estimates are also made of the strength of the electron-phonon coupling for longitudinal phonons which propagate along the molecular stacks.

A stereoselective synthesis of the tetrahydrofuran unit in ionomycin

Abstract The tetrahydrofuran unit corresponding to carbons 23 to 32 of the calcium ionophore, ionomycin, was prepared by a stereoselective permanganate cyclization of the ( Z , Z )-diene 5.

The synthesis of 14-membered macrocyclic ethers

Abstract As part of an ongoing study of the chemistry of macrocyclic compounds 14-membered macrocyclic ethers with a variety of methyl substitution patterns were synthesized. The preparation of these macrocyclic ethers involved either the Baeyer-Villiger ring expansion of a cyclic ketone or the macrolactonization of a hydroxy acid to give a lactone. The lactone carbonyl was removed either by conversion to an intermediate thionolactone obtained by reaction with Lawessons reagent and reduction or by direct reduction using a boron trifluoride etherate mediated sodium borohydride reaction.

The regioselective deprotonation of conjugated esters

Abstract A stereospecific synthesis of the E and Z esters of C–4 deuterated 3-methyl-2-butenoic acid from methyl acetoacetate is reported; the labelled methyl 3-methyl-2-butenote is regioselectively deprotonated syn to the ester group under kinetic conditions.

The stereospecific formation of an exocyclic alkene by a consecutive radical cyclization-elimination

The iodovinylstannanes 4 and 5 were prepared by the conjugate addition of the tri-n-butyltin moiety to a substituted propiolic ester. Compounds 4 and 5 underwent a radical cyclization-elimination reaction to stereospecifically generate an exocyclic alkene.

Photoelectron Spectrum and Electronic Structure of Tetrathiofulvalene (TTF)

The electronic structure of tetrathiofulvalene (TTF) has been determined from its photoelectron spectrum and the photoelectron data for the tetrahydro derivative of TTF and 1,3-dithiolane. Correlat...

Synthesis of the three isomeric components of San Jose scale pheromone

Abstract The three isomeric components of the San Jose scale pheromone have been synthesized stereospecifically from a common intermediate β-keto ester.

Synthesis of isoprenoid natural products from β-keto esters

Abstract The anions of β -keto esters were reacted with diethyl phosphorochloridate to yield the corresponding enol phosphate. These enol phosphates were coupled with lithium dimethylcuprate to give the resulting β -methyl α, β -unsaturated ester stereoselectively and in good yield. When combined with the β -alkylation of the β -keto ester dianions this overall sequence results in the stereoselective and regioselective incorporation of an isoprene moiety in a synthetic sequence. This transformation has been applied in the synthesis of ( E,E )-10-hydroxy-3,7-dimethyldeca-2,6-dienoic acid (butterfly compound), Latia luciferin, and mokupalide.

Modeling the interaction between FK506 and FKBP12: A mechanism for formation of the calcineurin inhibitory complex

FK506 is a naturally occurring immunosuppressant whose mode of action involves formation of an initial complex with the cytosolic protein FKBP12. The composite surface of this complex then binds to and inhibits the protein phosphatase calcineurin (PP2B). To investigate why FK506 does not inhibit calcineurin directly we have conducted molecular modeling and conformational studies on published structures of FK506 both alone and in complex with FKBP12. From studies of the structure of FK506 in CDCl3 and Z-Arg32-ascomycin in water (a water soluble analogue of FK506) we suggest that the FK506 molecule can be viewed as consisting of three separate regions. The pipecolate region which extends from C24 to C10 including the pipecolate ring shows strongly conserved conformation in both solvents. The loop region which extends from C25 to C16 shows general conservation of the loop structure and the pyranose region made up of the pyranose ring and C15-C17 which shows highly variable conformation depending on solvent. Comparison of the structure of Z-Arg32-ascomycin in water with structures of FK506 bound to FKBP12 indicate that the conformation of the pipecolate region is conserved during the binding process. The conformation of the loop region was generally conserved but a significant reduction (approximately 1.7 A) in the diameter of the loop in the bound structure was observed. The conformation of the pyranose ring and C15-C17 region was found to be significantly altered in the bound structure resulting in displacements of the C13 and C15 methoxyl groups of 2.8 and 3.5 A, respectively. From computer models and molecular dynamics simulations of interactions between FK506 and FKBP12 we suggest that the conformational changes observed in bound FK506 are induced by the interaction between the 80s loop of FKBP12 and the pyranose ring of FKBP12. These interactions result in the formation of a complex with the both correct shape and surface polarity for interaction with calcineurin.

Raman spectra of tetrathiofulvalene (TTF)

Abstract The Raman spectra of TTF and d 4 -TTF has been obtained on the powder and benzene solution. Preliminary assignments to several bands can be made from depolarization studies, isotope shifts and analogy to related systems.