In a prototypical ferromagnet (Ga,mn)As based on a III-V semiconductor, substitution of divalent mn atoms into trivalent Ga sites leads to severely limited chemical solubility and metastable specimens available only as thin films. The doping of hole carriers via (Ga,mn) substitution also prohibits electron doping. To overcome these difficulties, masek et al. theoretically proposed systems based on a I-II-V semiconductor LiZnAs, where isovalent (Zn,mn) substitution is decoupled from carrier doping with excess/deficient Li concentrations. Here we show successful synthesis of Li 1 + y (Zn 1 − x mn x )As in bulk materials. Ferromagnetism with a critical temperature of up to 50 K is observed in nominally Li-excess (y = 0.05-0.2) compounds with mn concentrations of x = 0.02-0.15, which have p-type metallic carriers. This is presumably due to excess Li in substitutional Zn sites. semiconducting LiZnAs, ferromagnetic Li(Zn,mn)As, antiferromagnetic LimnAs, and superconducting LiFeAs systems share square lattice As layers, which may enable development of novel junction devices in the future.

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A fully synthetic anticancer vaccine 2 has been prepared via bio-conjugation of unimolecular pentavalent construct 1 – containing five prostate and breast cancer associated carbohydrate antigens, Globo-H, GM2, STn, TF and Tn – to maleimide-modified carrier protein KLH. An improved conjugation protocol has been developed, which allowed us to obtain a higher epitope ratio of the unimolecular pentavalent glycopeptide antigen to the carrier protein (505/1 versus 228/1 for the previous version). KLH conjugate 2 has been subsequently submitted to preclinical immunogenic evaluation in mice in the presence of QS-21 as an adjuvant. Through standard ELISA assay, this vaccine candidate showed high promise in inducing IgG and IgM antibodies against each of the five individual carbohydrate antigens. In addition, FACS analysis indicated that these antibodies were able to react with MCF-7 breast cancer cell lines expressing these five carbohydrate antigens.

An approach to the asymmetric synthesis of the azaphilone natural products is reported involving copper-mediated enantioselective oxidative dearomatization of o-alkynylbenzaldehydes. The approach was successfully applied to the synthesis of (-)-S-15183a and several unnatural azaphilones.

A method by which to accomplish formal threonine ligation has been developed. The method accomplishes ligations of two peptide domains. We have also demonstrated the ability to successfully ligate two independent glycopeptide domains.

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The bicyclo[2.2.2]octenone skeleton is found in a number of natural products (Figure 1) including homodimers 1 2 and 2 (aquaticol), 3 and the hetero adduct chamaecypanone C (3). 4 While Diels-Alder cycloaddition of 2,4-cyclohexadienones and ortho-quinols with activated alkenes has frequently been used for the synthesis of bicyclo[2.2.2]octenones, 2,4-cyclohexadienones also have a high propensity to undergo spontaneous [4+2] We first investigated oxidation of the 2,5-disubstituted phenol carvacrol (4) using conditions previously reported for 2,4-dihydroxybenzaldehyde substrates enroute to the azaphilones 8 (Table 1, entry 1). In the event, reaction of 4 with a [(−)-sparteine] 2 Cu 2 O 2 (PF 6 ) 2 complex and N,N-diisopropylethylamine (DIEA) in CH 2 Cl 2 at −78 °C (16 h) afforded a mixture of the [4 +2] dimer (3S,10S)-1 in 25% isolated yield (99% ee by chiral HPLC analysis) and biaryl coupling product 5 (23%). 9 The backbone structure and absolute configuration of (3S, 10S)-1 were determined by comparison to NMR and CD spectral data reported for natural product (3R,10R)-1. 2, 10Further optimization studies revealed that use of LiHMDS to generate the phenolate in THF as solvent, 11 followed by oxidative dearomatization, cleanly afforded dimer 1 in 58% isolated yield (> 99% ee) with a trace amount of biaryl formation (Table 1, entry 2). Use of DIEA as base in THF (entry 3) also led to preferential formation of dimer 1. This result, along with reactions in propionitrile (entry 4) and acetone (entry 5), revealed a strong solvent effect for the reaction. Solvent and ligand effects reported in the literature 12 have generally been attributed to the equilibrium of binuclear copper-peroxo (P, μ-η 2 :η 2 -peroxodicopper(II)) and copper-oxo (O, bis(μ-oxo)dicopper(III)) complex forms. 13, 14 In the case at hand, the solvent effects may be rationalized by greater levels of the corresponding radical abstracting 15 [(−)-sparteine] 2 bis(μ-oxo)dicopper(III) (O) complex in CH 2 Cl 2 and the electrophilic μ-η 2 :η 2 -peroxodicopper(II) (P) complex in THF. Although evaluation of alternative counterions 16 (e.g. BF 4 − , OTf − , Cl − ) to favor formation of the corresponding P complex did not show substantial improvement over PF 6 −,10 we found that pre-formation of the phenolate with LiOH E-mail: porco@bu.edu. To evaluate the scope and limitations of this methodology, a number of phenol substrates were transformed into lithium phenolates and subsequently subjected to copper-mediated oxidative dearomatization ( Table 2). Use of 2,5-dimethyl and 2-methyl-5-tert-butyl substituted phenols 6 (entry 1) and 7 (entry 2), led to the production of [4+2] dimers 8 and 9 in high enantioselectivity, with a noticeable lower conversion observed for substrate 6. Substrate 10 (entry 3) bearing an electrondonating methoxy group at C5 was also successfully converted into dimer 11 after thermolysis of the crude monomer. 10 Attempted oxidation of 2,5-disubstituted phenols with electron-withdrawing groups at C5 gave poor conversion.10 Phenol 12 bearing...

An approach for direct synthesis of biologically significant 2-deoxy-β-glycosides has been developed via O-alkylation of a variety of 2-deoxy-sugar-derived anomeric alkoxides using challenging secondary triflates as electrophiles. It was found a free hydroxyl group at C3 of the 2-deoxy-sugar-derived lactols is required in order to achieve synthetically efficient yields. This method has also been applied to the convergent synthesis of a 2-deoxy-β-tetrasaccharide.