Some Diels–Alder adducts of 6-vinyl-1-oxa-4-thiaspiro[4.5]dec-6-ene

6-Vinyl-1-oxa-4-thia­spiro­[4.5]­dec-6-ene has been reacted with dienophiles, such as N-phenyl­male­imide (NPM), N-methyl­triazoline-2,5-dione (MTAD) and di­methyl­acetyl­ene di­carboxyl­ate (DMAD), to assess the 1,3-diastereofacial selection caused by the acetal function. In each case, a mixture of two diastereoisomers was produced. The crystal structures of the products of the addition of NPM and MTAD syn to the acetal oxy­gen, 2-phenyl-2,3,3a,4,5,5a,6,7,8,9,9a,9b-dodeca­hydro-1H-benz­[e]­iso­indole-6-spiro-2′-[1′,3′]­oxa­thiol­ane-1,3-dione, C₂₀H₂₁NO₃S, (IIa), and 2-methyl-5,7,8,9,10,10a-hexa­hydro-1H-1,2,4-triazolo­[1,2-a]­cinnoline-7-spiro-2′-[1′,3′]­oxa­thiol­ane-1,3-dione, C₁₃H₁₇N₃O₃S, (IIIa), respectively, and the product of the addition of DMAD syn to the acetal sulfur, di­methyl 1,2,3,4,4a,7-hexa­hydro­naphthalene-1-spiro-2′-[1′,3′]­oxa­thiol­ane-5,6-di­carboxyl­ate, C₁₆H₂₀O₅S, (IVb), have been determined. All three structures are composed of independent mol­ecules separated by normal van der Waals distances. The 1-oxa-4-thia heterocyclic ring has an envelope conformation in the three structures and the S—Csp³ bond distances differ significantly from each other, as observed in comparable structures; the remaining molecular dimensions are as expected.     

Recent Advances in the Applications of Nanotechnology and Nanomaterials in the Petroleum Industry: A Descriptive Review

Nanotechnology applications are rapidly expanding in various fields because of its unique qualities, such as a large surface area. Also, the synthetic changes can be utilized to alter nanomaterial to fit into specialized necessities. From the last decade there is a tremendous increase in the utilization of nanotechnology and nanomaterials in the petroleum industry. The current review's main objective is to summarize numerous nanoparticle applications in the field of petroleum, bio-fuel formation, and clean-up treatments of oil spill-related issues with their existing challenges that may help improve further research.     

Differentiation of diastereomeric conduramine derivatives under electron ionization and chemical ionization mass spectral conditions

Diastereomeric conduramine derivatives, i.e., (1R,2S,3R/S,6S)-6-(N-carbomethoxyamino) 1,2-O-isopropylidenecyclohex-4-ene-1,2,3-triol (1 and 2) and their O-acetyl derivatives (3 and 4), were studied using gas chromatography (GC) with electron ionization (EI) and chemical ionization (CI). The EI mass spectra of diastereomeric pairs show consistent differences in the relative abundances of characteristic ions. The EI fragmentation patterns are based on precursor/product ion spectra, high-resolution mass spectrometry (HRMS) and deuterium labelling. The CI spectra show differences from the EI spectra, and the isobutane/CI spectra are much simpler than the methane/CI spectra. The differences shown in the CI spectra are similar to those shown in the product ion spectra of [M+H](+) ions generated under electrospray ionization (ESI) conditions. Theoretical calculations are performed to understand the observed differences. The differences in the relative stabilities of molecular ions, or protonated molecules at different sites, can explain the observed differences in the spectra.     

Cell and protein compatibility of parylene-C surfaces

Parylene-C, which is traditionally used to coat implantable devices, has emerged as a promising material to generate miniaturized devices due to its unique mechanical properties and inertness. In this paper we compared the surface properties and cell and protein compatibility of parylene-C relative to other commonly used BioMEMS materials. We evaluated the surface hydrophobicity and roughness of parylene-C and compared these results to those of tissue culture-treated polystyrene, poly(dimethylsiloxane) (PDMS), and glass. We also treated parylene-C and PDMS with air plasma, and coated the surfaces with fibronectin to demonstrate that biochemical treatments modify the surface properties of parylene-C. Although plasma treatment caused both parylene-C and PDMS to become hydrophilic, only parylene-C substrates retained their hydrophilic properties over time. Furthermore, parylene-C substrates display a higher degree of nanoscale surface roughness (>20 nm) than the other substrates. We also examined the level of BSA and IgG protein adsorption on various surfaces and found that surface plasma treatment decreased the degree of protein adsorption on both PDMS and parylene-C substrates. After testing the degree of cell adhesion and spreading of two mammalian cell types, NIH-3T3 fibroblasts and AML-12 hepatocytes, we found that the adhesion of both cell types to surface-treated parylene-C variants were comparable to standard tissue culture substrates, such as polystyrene. Overall, these results indicate that parylene-C, along with its surface-treated variants, could potentially be a useful material for fabricating cell-based microdevices.     

Domino carbocationic rearrangement of alpha-[bis(methylthio)methylene]alkyl-2-(3/2-indolyl) cyclopropyl ketones

Domino carbocationic rearrangement of a number of substituted 3- and 2-indolylcyclopropyl ketones with an alpha-bis(methylthio)methylene group in the presence of various protic/Lewis acids yields a variety of products, mainly the pentaleno fused indoles and the carbazole derivatives.     

Stereoselective formal total synthesis of (+)-methynolide

A highly stereoselective and convergent formal total synthesis of (+)-methynolide is described. The salient features of this synthesis have been the construction of the C1-C7 and C8-C11fragments via a desymmetrization approach, Sharpless asymmetric epoxidation of an allyl alcohol, respectively, and linkage of both the fragments by Nozaki-Hiyama-Kishi reaction.     

Stereoselective synthesis of the phytotoxic nonenolide herbarumin-I from l-ascorbic acid

A stereoselective synthesis of herbarumin-I in 22% overall yield, starting from l-ascorbic acid derived (S)-2,3-O-isopropylidine glyceraldehyde as a chiral template is reported. Stereoselective allylation and vinylation to control the required stereogenic centres and macrolactonisation followed by a ring-closing metathesis (RCM) are the key steps.     

New cassane butenolide hemiketal diterpenes from the marine creeper Caesalpinia bonduc and their antiproliferative activity

Two new cassane butenolides, caesalpinolide A (1) and B (2), epimeric at the hemiketal position were isolated from the marine creeper Caesalpinia bonduc. The structures were elucidated by the analysis of spectroscopic data and relative stereochemistry was assigned on the basis of ROESY correlations. Compounds 1 and 2 were found to inhibit MCF-7 breast cancer cell lines with IC₅₀ values of (μM) 12.8 and 6.1, respectively, along with the inhibition of endometrial and cervical cancer cell lines.     

Effect of overtaking disturbances on strong cylindrical shock in a self-gravitating gas

The effect of overtaking disturbances on the propagation of strong cylindrical shock in a self-gravitating gas has been studied by an approximate technique developed by Yadav (1992). Assuming an initial density distribution law ase _o=er^–w , wheree is the density at the axis of symmetry andw is a constant, the analytical expressions for shock velocity and shock strengths modified by overtaking waves have been obtained. The results accomplished here have been compared with those for freely propagating shock.The conclusions arrived here agreed with experimental results.Finally, the modified expressions for the pressure, the density and the particle velocity immediately behind the shock have also been derived.