Total synthesis of (±)-sterpuric acid

The unusual sesquiterpenoid fungal metabolite sterpuric acid (1) has been assembled in 11 steps and 11% overall yield from the readily available vinyl sulfone 2.     

Comparative Study of the Synthetic Approaches and Biological Activities of the Bioisosteres of 1,3,4-Oxadiazoles and 1,3,4-Thiadiazoles over the Past Decade

The bioisosteres of 1,3,4-oxadiazoles and 1,3,4-thiadiazoles are well-known pharmacophores for many medicinally important drugs. Throughout the past 10 years, 1,3,4-oxa-/thiadiazole nuclei have been very attractive to researchers for drug design, synthesis, and the study of their potential activity towards a variety of diseases, including microbial and viral infections, cancer, diabetes, pain, and inflammation. This work is an up-to-date comparative study that identifies the differences between 1,3,4-thiadiazoles and 1,3,4-oxadiazoles concerning their methods of synthesis from different classes of starting compounds under various reaction conditions, as well as their biological activities and structure–activity relationship.     

Iron-mediated aromatic allylation

Electron rich aromatic and heteroaromatic compounds react with (n³-allyl)Fe(CO)₄BF₄ to produce allylated aromatics in moderate to good yields. Unsymmetrically substituted allyl complexes afford the corresponding butenyl-, 1,1-dimethylallyl-, cinnamyl-, and geranyl-derivatives with moderate to excellent regioselectivity and complete stereoselectivity.     

Formation of a bis-lactone from 3-O-acetyl-deoxycholic acid

By the action of dichloroethyl phosphate upon 3α-acetoxy-12α-hydroxy-5β-cholanic acid (1) in methylene chloride, unexpectedly, a bis-lactone2 was formed. Sodium methoxide catalyzed deacetylation of2 afforded 16-membered deoxycholic acid 24, 12'α: 24′, 12α-bis-lactone (3) whose structure was determined by an x-ray structural analysis.     

The 1,4 O→C silyl migrations of various 3-[(trialkylsilyl)oxymethyl]-furans and -thiophenes

Numerous 3-[(trialkylsilyl)oxymethyl]-furans and -thiophenes undergo a 1,4 O→C silyl migration when treated with n-BuLi/HMPA in THF or DME to produce 2-(trialkylsilyl)-3-(hydroxymethyl)-furans and -thiophenes in good yields.     

Amino acid derivatives that stabilized secondary structures of polypeptides—III. β-Enaminonitriles as analogs of secondary amides. The MCC group—1-acylamino-2-aminoalkyl-3-cyano-2-cyclopentenes as amino acid analogs.

The properties of β-cyanoenamines as analogs of amides are studied with derivatives of a rigid amino acid equivalent—Mcc = 1,2-diamino-3-cyanocyclopentene, prepared in two steps from methyl 2-(N-Boc-amino)-5-cyanopentanoate. Racemation of Mcc and incorporation into a cyclic pentapeptide are described.     

Gap states at organic-metal interfaces: A combined spectroscopic and theoretical study

A systematic understanding and controlling of gap states formed at the organic-metal interfaces is a key factor for fabricating functional organic-metal systems, as in case of heterojunctions in semiconductor devices. We report here the characterization of gap states near the Fermi level of metal substrate by metastable atom electron spectroscopy and first-principles density functional calculations. The gap states in organic-metal systems are classified into two types, i.e., chemisorption-induced gap states (CIGSs) and complex-based gap states (CBGSs). CIGSs can be further classified whether the metal wave function tails a short distance into the chemisorbed species with the exponential decay (damping type) or is exposed sufficiently to the chemisorbed species by mixing with the organic orbitals (propagating type). CIGSs observed in alkanethiolate and C₆₀ on Pt(1 1 1) are their typical examples, respectively. As a consequence, alkanethiolate serves as a poor mediator of metal wave function, whereas C₆₀ acts as a good mediator, which is responsible for tunneling mechanism and eventually electric conductivity in the relevant metal-organic-metal junctions. CBGSs are identified in bathocuproine films deposited on K-covered Au, where the K atoms migrate into the film to form an organic-metal complex. The CBGSs are distributed over the multilayer film, in contrast to the case of CIGS. With increasing film thickness, the CBGSs exhibit incommensurate energy shifts with the valence band top of the film, indicating that the Schottky-Mott model breaks down as evaluating charge transport in organic-metal systems.     

New synthesis of steroidal tetrahydrooxazin-2-ones

In the DMSO/NaHCO₃ system, 16α-aminomethyl-, 16α-benzylaminomethyl- and substituted benzylaminomethyl-3-methoxy-17β-tosyloxyestra-1,3, 5(10)-triene (3, 5a-k) do not undergo oxidation, but form a tetrahydrooxa-zin-2-one ring (7, 8a-k) via neighboring group participation. Under similar conditions, 16β-aminomethyl-3-methoxy-17β-tosylestra-1,3,5(10)-triene (4) decomposes into 16-methylene-3-methoxyestra-l,3,5(10)-trien-17-one (12).