High-resolution electron energy loss spectroscopy (HREELS) studies were performed to examine the reactions of 2-iodoethanol (ICH 2 CH 2 OH) on the Ag(110) surface. The goal of these experiments was to isolate and spectroscopically characterize a stable surface oxametallacycle, an intermediate previously proposed but never isolated in the chemistry of a variety of oxygenates, including epoxides. The hydroxyethyl intermediate (-CH 2 CH 2 OH), formed from initial carbon-iodine bond scission, decomposed at 263 K to yield a variety of volatile products as well as a surface oxametallacycle (-CH 2 CH 2 O-). The oxametallacycle intermediate, formed at 263 K, remained intact until 340 K, permitting spectroscopic characterization by HREELS. Density Functional Theory (DFT) calculations were employed to determine the fully optimized structure for the oxametallacycle on silver and to predict the infrared spectrum and molecular motions for that structure. The excellent agreement between the infrared spectrum predicted for an oxametallacycle incorporating two silver atoms and the experimental HREEL spectrum conclusively identifies the surface oxametallacycle. The principal reaction channel for this intermediate in temperature programmed desorption (TPD) experiments is coupling of two oxametallacycles to form the cyclic product γ-butyrolactone, rather than the anticipated ring closure pathway to form ethylene oxide. However, one of the vibrational modes predicted by DFT appears to be a possible reaction coordinate for the conversion of oxametallacycles to ethylene oxide.

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The commercial-scale synthesis of the DPP-IV inhibitor, saxagliptin (1), is described from the two unnatural amino acid derivatives 2 and 3. After the deprotection of 3, the core of 1 is formed by the amide coupling of amino acid 2 and methanoprolinamide 4. Subsequent dehydration of the primary amide and deprotection of the amine affords saxagliptin, 1. While acid salts of saxagliptin have proven to be stable in solution, synthesis of the desired free base monohydrate was challenging due to the thermodynamically favorable conversion of the free amine to the six-membered cyclic amidine 9. Significant process modifications were made late in development to enhance process robustness in preparation for the transition to commercial manufacturing. The impetus and rationale for those changes are explained herein.

Reactions of maleic anhydride over TiO 2 (001) single crystal surfacesThe adsorption and reaction of 2-iodoethanol ͑IEtOH͒ on a clean Ag͑110͒ surface were studied under ultrahigh vacuum conditions using temperature programmed deposition ͑TPD͒. Under these conditions alcohols are typically unreactive on the clean Ag͑110͒ surface. Replacement of one of the ␤ hydrogens with a weakly bound ͑53 kcal/mol͒ iodine atom, however, opens a channel for IEtOH decomposition by initial carbon-iodine scission. TPD results indicate that there are two major reaction channels at 263 and 340 K for IEtOH decomposition on the clean Ag͑110͒ surface. The reaction intermediates that give rise to these two pathways were deduced based upon the products observed, the overall product stoichiometry, and the desorption temperatures of the products. The 263 K reaction channel has an overall stoichiometry of C 2 H 5 O, corresponding to a hydroxyethyl intermediate. The hydroxyethyl intermediate undergoes a ␤-hydride elimination and C-O scission, ultimately yielding volatile acetaldehyde, ethylene, water, ethanol, and another surface intermediate that decomposes at 340 K. Unlike unsubstituted alkyl groups on clean Ag͑111͒ and Ag͑110͒ which couple to form alkanes, there is no evidence for hydroxyethyl coupling to give butanediol. Thus, the hydroxyethyl cannot be treated simply as a substituted alkyl group; that is probably due to interactions between oxygen and the surface. The stoichiometry of the products released at 340 K, C 2 H 4 O, is suggestive of an oxametallacycle intermediate. The products of this reaction channel are the same as the 263 K channel with the addition of a cyclic ester product, ␥-butyrolactone. This species has not previously been synthesized from a C 2 precursor in ultrahigh vacuum, and its observation suggests that surface oxametallacycle chemistry may be richer than previously recognized.

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In this study, the effects on antioxidant activity and structure change of corn peptides (CPS) with 10 to 30 kDa molecular weight (MW) treated by pulsed electric field (PEF) technology were investigated. 2, 2-diphenyl-1-picrylhydrazyl (DPPH) inhibition was used to evaluate the antioxidant activity of CPS. Response surface methodology (RSM) was used to investigate the effects of PEF treatment parameters on antioxidant activity of CPS. The optimal conditions were as follows: concentration of CPS 10 mg mL −1 , electric field intensity 15 kV cm −1 , and pulse frequency 2,000 Hz. Under the optimized conditions, the DPPH inhibition of CPS increased 32.1 %, compared to the sample untreated. And mid-infrared spectroscopy (MIR) was used for analyzing the structure change of CPS. The results showed that PEF technology could obviously increase the DPPH inhibition of CPS under the optimized conditions (P<0.05).