Rh2(OAc)4 catalyzed substrate selective [4+2]/[2+2] cycloaddition of acylketenes: a highly chemo- and regioselective synthesis of spiro(oxindolyl)oxazinones and β-lactams

A rhodium(II) catalyzed [4+2]/[2+2] cycloaddition reaction of N-protected isatin-3-arylimine with acylketene derived from α-diazocarbonyl compounds has been achieved for the first time for the preparation of a novel class of spiro(oxindolyl)oxazinone and spiro(oxindolyl)-β-lactam derivatives.     

l-Proline catalyzed efficient one-pot three-component aza-Diels–Alder reactions on nitrostyrylisoxazoles: a facile synthesis of new isoxazolyl tetrahydroquinolines and isoxazolo[2,3-a]pyrimidines

l-Proline acts as an efficient organocatalyst and found to promote one-pot three-component aza-Diels–Alder reaction of aryl or isoxazole imines formed in situ from aromatic or isoxazoleamines and aromatic aldehydes with nitrostyrylisoxazoles to afford the isoxazolyl tetrahydroquinolines or isoxazolo[2,3-a]pyrimidines, respectively, in excellent yields at ambient temperature under neutral conditions.     

A facile synthesis of melatonergic antidepressant agomelatine

Agomelatine was synthesized from 8-aminonaphthalen-2-ol by diazotization-iodination, formylation, C–C bond formation by nitroaldol and Pd/C hydrogenation of β-nitrovinylnaphthalene followed by N-acetylation. The route reported employs readily and commercially viable starting materials and reagents, and can potentially be utilized for process synthesis of agomelatine.     

Triflic acid-promoted aza-Prins-Ritter reaction sequence: a novel synthesis of 4-amidopiperidine derivatives

4-Amidopiperidine derivatives have been prepared for the first time in good yields and with high selectivity by means of aza-Prins-Ritter reaction sequence using 1.2 equiv of triflic acid under mild reaction conditions.     

Identification of mutant firefly luciferases that efficiently utilize aminoluciferins

Firefly luciferase-catalyzed light emission from D-luciferin is widely used as a reporter of gene expression and enzymatic activity both in vitro and in vivo. Despite the power of bioluminescence for imaging and drug discovery, light emission from firefly luciferase is fundamentally limited by the physical properties of the D-luciferin substrate. We and others have synthesized aminoluciferin analogs that exhibit light emission at longer wavelengths than D-luciferin and have increased affinity for luciferase. However, although these substrates can emit an intense initial burst of light that approaches that of D-luciferin, this is followed by much lower levels of sustained light output. Here we describe the creation of mutant luciferases that yield improved sustained light emission with aminoluciferins in both lysed and live mammalian cells, allowing the use of aminoluciferins for cell-based bioluminescence experiments.     

Synthetic studies of stereocalpin A and its C5-epimer: total synthesis of 11-epi- and 5,11-diepi-stereocalpin A

This Letter describes the synthetic studies of stereocalpin A and its C5-epimer. After various cyclization attempts, successful macrolactamization at 9-10 position was tried inorder to obtain stereocalpin A and its C5-epimer, which were accompanied by complete racemization and resulted in the synthesis of 11-epi- and 5,11-diepi-stereocalpin A. Highly functionalized octanoic acid motif of the depsipeptide was constructed by applying Paterson’s aldol methodology, owing to its diversity in synthesizing various analogs of aliphatic acid.     

Accumulation of Poly[(<Emphasis Type=Italic>R</Emphasis>)-3-hydroxyalkanoates] in <Emphasis Type=Italic>Enterobacter cloacae</Emphasis> SU-1 During Growth with Two Different Carbon Sources in Batch Culture

Polyhydroxyalkanoates (PHAs) are polymers of hydroxyalkanoate, which are accumulated by many bacteria as food storage material under excess carbon source and limited nitrogen source. In our study, Enterobacter cloacae SU-1 isolated from the rhizospheric soil of Arachis hypogea was allowed to grow as batch culture in minimal media containing either glucose or lactose, and the pattern of PHA accumulation by E. cloacae SU-1 was studied. E. cloacae SU-1 was found to accumulate 94% of PHA/dry weight of the organism in 8 g/l lactose-containing medium. When the monomeric units of PHA of E. cloacae SU-1 was analyzed by gas chromatography, it was also found to accumulate medium chain length PHA 3-hydroxyoctanoate (3HO)/3-hydroxyhexanoate (3HH) in the presence of glucose and lactose, but the ratio of these monomers differed as 11:1 and 6:1, respectively.     

Silver(I)‐Catalyzed Enantioselective [3+2]‐Cycloaddition Reaction of α‐Silylimines: A Facile Route to Quaternary‐Carbon‐Rich Scaffolds

A silver‐catalyzed highly enantioselective 1,3‐dipolar cycloaddition reaction of α‐silylimines with pyrone‐based trisubstituted olefins was developed affording bi‐ and tricyclic α‐quaternary‐carbon‐rich pyrano‐pyrrolidines in excellent yields. The tricyclic benzopyrone adducts thus obtained were efficiently transformed into highly complex tetracyclic scaffolds supporting four consecutive stereogenic centers with three quaternary carbons.