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We describe the syntheses of thiophene, cyclopentadienone and dimethylketalcyclopentadienone derivatives and their single molecule electrical conductivities. The ketone had the lowest conductivity of the three, although it has some antiaromaticity. The carbonyl group is electron attracting and its ionization potential outweighs any conductivity increase that the antiaromaticity effect might bring.

For life to start on earth and elsewhere, it is critical that the building blocks—amino acids and sugars—be in predominant homochiral form. Over the past century the origin of terrestrial prebiotic homochirality has been the subject of many speculations. In this Letter I summarize the experimental evidence for ways in which some meteoritic components could have led to the dominance of l amino acids and d sugars on earth, and the most likely way in which the original chiral excesses in the meteorites were formed.

For life to start on earth and elsewhere, it is critical that the building blocks—amino acids and sugars—be in predominant homochiral form. Over the past century, the origin of terrestrial prebiotic homochirality has been the subject of many speculations. In this Letter I summarize the experimental evidence for ways in which some meteoritic components could have led to the dominance of l amino acids and d sugars on earth, and the most likely way in which the original chiral excesses in the meteorites were formed.

Chiral polyamines can be utilized for a variety of potential applications, ranging from asymmetric catalysis to nonviral gene delivery systems for DNA and RNA. They can also be utilized to solubilize carbon nanotubes. Thus, methods for the straightforward synthesis of chiral polyamines are needed. We present herein two synthetic strategies for accessing chiral polyamines. The potential of these chiral amines to catalyze two organic reactions with a high degree of chiral induction was also explored.Text: Chiral polyamines have been utilized for a variety of applications. First, polyamines are polycationic at neutral pH; as such, they interact strongly with both DNA and RNA.1 They can therefore be utilized as effective nonviral gene delivery agents.2 Second, chiral polyamines are efficient catalysts for various organic transformations.3 Polyamines have also been used to solubilize carbon nanotubes.4 Finally, chiral polyamines are excellent ligands for many transition metals.5 Due to their numerous applications, high-yielding synthetic strategies for their preparation are in great demand. We present herein two synthetic strategies for accessing chiral polyamines, and the potential of these chiral amines to catalyze two organic reactions.

There is overwhelming evidence that meteorites bring α-methylated amino acids to earth with some l (S) enantiomeric excess. How does that get transferred into normal biological molecules? In this brief account, we show that an α-methylated amino acid, d (R)-α-methylvaline, can react with pyruvate and phenylpyruvate salts in dry mixtures to form alanine and phenylalanine with l enantiomeric excesses, under sensible prebiotic conditions. Thus the meteoritic l (S) excesses of this compound would produce excess d -alanine and d -phenylalanine, which are found in some organisms.

Amine boranes bearing hydrophobic substituents were used to reduce aryl ketones in competition with a methyl ketone. Their high stability in protic solvents combined with their ease of preparation made amine boranes useful compounds in the study of hydrophobically directed selective reductions. Several characteristics of the reducing agent were found to be important in determining the reaction selectivity, including available hydrocarbon surface area, degree of fluorination, and proximity of the hydrophobic group to the active hydrides.

A novel catalyst has been synthesized in which a manganese–porphyrin unit is linked to four hydrophobic cyclophane binding groups. Relative to a previous catalyst in which the binding groups were cyclodextrins, the new catalyst shows somewhat higher catalytic turnovers before it is destroyed, but less selective product formation.

A series of cyclodextrin trimers and dimers were prepared and examined as binders for appropriate trimeric and dimeric aminoacid amides. Tritopic binding was stronger than ditopic binding, although the free energies were not strictly additive. Such trimers are attractive prospects for the binding of polypeptides and proteins.

Equilenin acetate and dihydroequilenin acetate were oxidized with iodosobenzene and a rhodium(III) porphyrin catalyst. The selectivity of the reactions differs from that with the corresponding Mn(III) catalyst, or from that of free radical chain oxidation.

The Cu(II) complex of a cyclodextrin dimer linked by a bipyridyl unit catalyzes the hydrolysis of an unactivated doubly-bound benzyl ester.

A catalyst combining a cyclodextrin binding group with a bound zinc cation and an oxime anion cleaves bound esters in a two step process. A catalyst combining a cyclodextrin binding group with a bound zinc cation and an oxime anion cleaves bound esters in a two step process. Download full-size image

A variety of regioisomeric bifunctionalized β-cyclodextrins derivatized with an imidazole and a metal ligand tris(2-aminoethyl)amine (tren) group were prepared. As their Zn2+ complexes, these compounds show bifunctional catalysis of phosphate hydrolysis with a regioisomeric preference.

A variety of mono- and unsymmetrical bifunctional β-cyclodextrins have been developed as efficient mimics of class I aldolases, some of which show a large rate acceleration and substrate selectivity.

A metalloporphyrin has been synthesized carrying a beta-cyclodextrin group on tetrafluorophenyl rings at the four meso positions of the porphyrin. It performs the selective hydroxylation of an androstanediol derivative with complete positional selectivity and 187 turnovers.

Cobalamin covalently tethered to β-cyclodextrin was synthesized as a methylmalonyl-CoA mutase mimic. The artificial enzyme is capable of discriminating between two substrates containing different binding groups.

The intramolecular aldol condensation of a dialdehyde carrying a t-butylphenyl group is almost random with simple imidazole buffer catalysis, but shows a 97% preference for a single regiochemistry of cyclization when the reaction is catalyzed by the imidazole groups of a cyclodextrin-bis-imidazole enzyme mimic.

Two water soluble cyclophane dimers have been prepared, and their binding properties examined. With a range of bidentate guests, the affinities of the new dimeric cyclophanes were similar to those of the monomeric analog.

Kinetic studies show that the benzoin condensation catalyzed by 3,4,5-trimethylthiazolium iodide and triethylamine in DMSO has a transition state with two benzaldehyde and one thiazolium components, while the conversion of nitrobenzaldehyde to the thiazolium adduct is kinetically first order in thaizolium salt and aldehyde. These findings exclude proposals that thiazolium dimers are the true catalytic species.

Double binding of a steroid substrate to our previously described mimic of the cytochrome P-450 enzymes hydroxylates carbon 9 of the steroid, but with a second significant product. The geometry has been adjusted with new catalysts that show high selectivity and excellent turnover for the C-9 hydroxylation.

Steroid esters of quinoline and acridine carboxylic acids can undergo template directed delivery of chlorine atoms to a particular steroid hydrogen even though chlorination selectivity studies with 2,3-dimethylbutane suggest that the bonding in the chlorine complex is probably different from that with pyridine templates.

The racemase activity of pyridoxal enzyme models is selectively increased in preference to transaminase activity by the attachment of rigid basic groups.

Protected phosphoramidites of 3′-deoxyadenosine and 3′-deoxy-5-methyluridine have been synthesized, and used in solid phase synthesis of 3′-deoxyoligonucleotides with the unusual 2′–5″ linkage.

17-Chlorosteroids, produced by template-directed halogenation of 9-fluoro 11-oxygenated cholestanols that are themselves produced by template methods, are converted to their 17-keto analogs in high yields (85–91 %) after HCl elimination with DBU, followed by ozonolysis.

1,2,3-tris(4-pyridyl)cyclopropene carrying a 3-benzenesulfonyl group has been synthesized, and other cyclopropenes carrying pyridine and pyridinium rings. Some of these can be converted to hexa(4-pyridyl)benzene and its pyridinium analog.

The rate of acylation of β-cyclodextrin by substituted phenyl esters of adamantanepropiolic acid shows a normal dependance on the basicity of the leaving group. This shows that the abnormal behavior in acylation by ferroceneacrylate esters can be solved with additional flexibility, which allows the geometry to change in response to the demands of the reaction path.

A cyclopentenyl trication stabilized by five propylamino substituents was prepared, as well as a related cyclopentadienone derivative.

A water soluble tin hydride has been synthesized carrying three methoxyethoxypropyl groups. It reduces various alkyl halides in water, or in organic solvents.