Photolytic-interference-free, femtosecond two-photon fluorescence imaging of atomic hydrogen

We discuss photolytic-interference-free, high-repetition-rate imaging of reaction intermediates in flames and plasmas using femtosecond (fs) multiphoton excitation. The high peak power of fs pulses enables efficient nonlinear excitation, while the low energy nearly eliminates interfering single-photon photodissociation processes. We demonstrate proof-of-principle, interference-free, two-photon laser-induced fluorescence line imaging of atomic hydrogen in hydrocarbon flames and discuss the method's implications for certain other atomic and molecular species.     

Formal synthesis of Pellasoren – A

A convergent and highly stereoselective formal synthesis of Pellasoren – A is described. The salient features of the synthesis are the utilization of enzymatic desymmetrization, Crimmin’s non-Evans syn aldol, Lindlar’s and Wittig reaction.     

Efficient Regio‐ and Stereoselective Conversions of Oxiranes and Aziridines into β‐(Nitrooxy)‐Substituted Alcohols and Amines by Using Bismuth Nitrate

Oxiranes and aziridines efficiently undergo ring opening with bismuth nitrate at room temperature to furnish the corresponding β‐(nitrooxy)‐substituted alcohols and amines respectively. The conversions are highly regio‐ and stereoselective and afford the nitrooxy‐compounds in excellent yields within a short period of time.     

Origin and removal of adducts (molecular mass = 98 u) attached to peptide and protein ions in electrospray ionization mass spectra

Electrospray ionization of peptides and proteins often produces intense adduct ions resulting from the attachment of a moeity with mass 98 u. The formation of these adduct ions results in a substantial reduction in the mass spectrometric sensitivity and an undesirable increase in the complexity of the mass spectra. In the present study it was shown that the removal of the attached adducts from peptide and protein ions can be affected by collisional activation and that the adducts arise from the attachment of sulfuric acid or phosphoric acid to peptide and protein ions. When sulfate and phosphate ions are removed from the samples by chemical means, adduct free ions are obtained from proteins yielding spectra with improved quality and sensitivity.     

Some NP-complete problems in quadratic and nonlinear programming

In continuous variable, smooth, nonconvex nonlinear programming, we analyze the complexity of checking whether

1. a given feasible solution is not a local minimum, and
2. the objective function is not bounded below on the set of feasible solutions.

We construct a special class of indefinite quadratic programs, with simple constraints and integer data, and show that checking (a) or (b) on this class is NP-complete. As a corollary, we show that checking whether a given integer square matrix is not copositive, is NP-complete.     

Highly regioselective ring opening of epoxides and aziridines using (bromodimethyl)sulfonium bromide

Epoxides and aziridines undergo ring opening efficiently with (bromodimethyl)sulfonium bromide at room temperature to form the corresponding β-bromohydrins and β-bromoamines, respectively. The conversions are highly regioselective and afford the products in excellent yields within a short period of time.     

Direct C-allylation of aryl-alkyl/glycosyl carbinols: facile synthesis of C-linked carbo-beta2-/gamma2-/delta2-amino acids

A facile ZrCl4-catalyzed direct allylation of the p-methoxyphenyl-alkyl/glycosyl carbinols at room temperature, and the conversion of the derived aryl-glycosyl-alkenes into hitherto unknown C-linked carbo-beta2-/gamma2-/delta2-amino acids is reported.     

Highly efficient one-pot synthesis of α-aminophosphonates using nanoporous AlSBA-15 catalyst in a three-component system

Research on Chemical Intermediates - Nanoporous AlSBA-15 catalysts with different nSi/nAl ratios (41, 129, and 210) were synthesized using a hydrothermal method. These catalysts were characterized...     

Synthesis of β‐Chlorohydrins in Water

2,4,6‐Trichloro‐1,3,5‐triazine (TCT, cyanuric chloride) was found to mediate the regio‐ and stereoselective ring opening of epoxides in H₂O in the presence of morpholine at room temperature to afford the corresponding β‐chlorohydrins in excellent yields (Table). The transformation is very simple, fast, efficient, and ecologically beneficial.     

Absolute control of helical handedness in quinoline oligoamides

The synthesis of quinoline-derived helically folded aromatic oligoamides functionalized by various chiral functions at their N-terminus is reported. When a (1S)-(-)-camphanyl moiety was introduced, it was found that helix handedness was completely shifted to right-handed helicity (de > 99%), in both protic and nonprotic solvents. The absolute helical sense and the de values were unambiguously characterized by using (1)H NMR, circular dichroism (CD), and X-ray crystallography. The crystal structure of these compounds allowed us to propose a rationale for the efficiency of helix handedness induction based on a combination of steric factors and intramolecular hydrogen bonding.