Synthesis of Optically Active 6-Alkynyl- and 6-Alkylpurines as Cytokinin Analogs and Inhibitors of 15-Lipoxygenase; Studies of Intramolecular Cyclization of 6-(Hydroxyalkyn-1-yl)purines

2005 ◽  
Vol 2005 (23) ◽  
pp. 4988-4994 ◽  
Author(s):  
Tom Christian Berg ◽  
Lise-Lotte Gundersen ◽  
Aud Berglen Eriksen ◽  
Karl E. Malterud
Keyword(s):  
Intramolecular Cyclization ◽  
Optically Active

Synthesis of Optically Active P-Chirogenic Ferrocene-Fused Benzophosphole by Diastereoselective Intramolecular Cyclization of Phosphanylferrocene Derivatives

Heterocycles ◽  
2009 ◽  
Vol 78 (12) ◽  
pp. 3001 ◽  
Author(s):  
Jyoji Kurita ◽  
Jun-ichi Hagiwara ◽  
Hiroshi Danjo ◽  
Masatoshi Kawahata ◽  
Naoki Kakusawa ◽  
...  
Keyword(s):  
Intramolecular Cyclization ◽  
Optically Active

Intramolecular Cyclization of Some Acyclic Nucleoside Analogs

1996 ◽  
Vol 61 (3) ◽  
pp. 442-457 ◽  
Author(s):  
Zlatko Janeba ◽  
Antonín Holý ◽  
Hana Votavová ◽  
Milena Masojídková
Keyword(s):  
Intramolecular Cyclization ◽  
Aqueous Ammonia ◽  
Sodium Hydride ◽  
Nucleoside Analogs ◽  
Oxidative Cyclization ◽  
Membered Ring ◽  
Optically Active ◽  
Cd Spectra ◽  
Acyclic Nucleoside ◽  
Derivatives Of

Reaction of stereoisomeric 8-bromo-9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines (8) with concentrated aqueous ammonia, sodium hydride, potassium tert-butoxide, or 1,8-diazabicyclo[5,4,0]undec-7-ene afforded 4e-O,8-anhydro-9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines 9 (derivatives of 1,3-oxazepino[2,3-e]adenine). The CD spectra of optically active stereoisomers of 9 have been studied and it was found that for threo isomers 9a and 9b their character corresponds to 5'-O,8-cycloadenosine. The compounds 9 were also prepared by oxidative cyclization of 9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines (7) with lead(IV) acetate in benzene. Reaction of 9-(4-hydroxybutyl)adenine (14) with lead(IV) acetate smoothly afforded the seven-membered ring derivative, 4'-O,8-anhydro-9-(4-hydroxybutyl)adenine (15); no anhydro products with five-, six-, and eight-membered ring were found. 2',3'-O-Isopropylideneinosine (16) reacted with lead(IV) acetate to give 5'-O,8-cyclo-2',3'-O-isopropylideneinosine (17) whereas 9-(4-hydroxybutyl)hypoxanthine (18) afforded no cyclic products.

Optical analysis of ink and other contaminants in process waters

TAPPI Journal ◽  
2012 ◽  
Vol 11 (8) ◽  
pp. 51-58
Author(s):  
ANTTI HAAPALA ◽  
MIKA KÖRKKÖ ◽  
ELISA KOIVURANTA ◽  
JOUKO NIINIMÄKI
Keyword(s):  
Optically Active ◽  
Process Water ◽  
Paper Machine ◽  
Optical Analysis ◽  
Direct Process ◽  
Active Components ◽  
Water Contaminants ◽  
Dependent Measurement ◽  
Measurement Methodology

Analysis methods developed specifically to determine the presence of ink and other optically active components in paper machine white waters or other process effluents are not available. It is generally more interest¬ing to quantify the effect of circulation water contaminants on end products. This study compares optical techniques to quantify the dirt in process water by two methods for test media preparation and measurement: direct process water filtration on a membrane foil and low-grammage sheet formation. The results show that ink content values obtained from various analyses cannot be directly compared because of fundamental issues involving test media preparation and the varied methodologies used to formulate the results, which may be based on different sets of assumptions. The use of brightness, luminosity, and reflectance and the role of scattering measurements as a part of ink content analysis are discussed, along with fine materials retention and measurement media selection. The study concludes with practical tips for case-dependent measurement methodology selection.

Microscopic Structure of Er-Related Optically Active Centers in Si

2003 ◽  
Vol 770 ◽  
Author(s):  
H. Przybylinska ◽  
N. Q. Vinh ◽  
B.A. Andreev ◽  
Z. F. Krasil'nik ◽  
T. Gregorkiewicz
Keyword(s):  
Ground State ◽  
Photoluminescence Spectrum ◽  
Zeeman Effect ◽  
Optically Active ◽  
Single Type ◽  
Active Centers ◽  
Mbe Growth ◽  
Spectral Components ◽  
Er Doped ◽  
Successful Observation

AbstractA successful observation and analysis of the Zeeman effect on the near 1.54 μm photoluminescence spectrum in Er-doped crystalline MBE-grown silicon are reported. A clearly resolved splitting of 5 major spectral components was observed in magnetic fields up to 5.5 T. Based on the analysis of the data the symmetry of the dominant optically active center was conclusively established as orthorhombic I (C2v), with g‼≈18.4 and g⊥≈0 in the ground state. The fact that g⊥≈0 explains why EPR detection of Er-related optically active centers in silicon may be difficult. Preferential generation of a single type of an optically active Er-related center in MBE growth confirmed in this study is essential for photonic applications of Si:Er.

Concise Synthesis of GB22 by Endo-Selective Siloxycyclopropane Arylation

2019 ◽  
Author(s):  
Hannah E. Burdge ◽  
Takuya Oguma ◽  
Takahiro Kawajiri ◽  
Ryan Shenvi
Keyword(s):  
Intramolecular Cyclization ◽  
Cross Coupling ◽  
Building Blocks ◽  
Ring Expansion ◽  
Dual Catalysis ◽  
Acid Labile

<div><div><div><p>The first synthesis of GB22 was accomplished by a con- cise, modular route. Two building blocks converged in a novel sp3-sp2 attached-ring coupling that used Ir/Ni dual-catalysis to reverse the regioselectivity of siloxycy- clopropane arylation. This cross-coupling proved general to access β-substituted tetralones via ring-expansion of indanone-derived siloxycyclopropanes. The congested, bridging rings of the GB alkaloids were completed using an aluminum-HFIP complex that effected intramolecular cyclization of an acid-labile substrate.</p></div></div></div>

Sign in / Sign up

Export Citation Format

Share Document