Concise synthesis of anti-HIV-1 active (+)-inophyllum B and (+)-calanolide A by application of (-)-quinine-catalyzed intramolecular oxo-Michael addition

(-)-Quinine-catalyzed intramolecular oxo-Michael addition (IMA) of 7-hydroxy-5-methoxy-8-tigloylcoumarins was developed for the enantioselective construction of 2,3-dimethyl-4-chromanone systems in the context of the asymmetric synthesis of anti-HIV-1 active Calophyllum coumarins. Combination of the IMA and MgI(2)-assisted demethylation of the 5-methoxy group along with isomerization of the formed chromanone systems as key steps successfully led to the concise synthesis of (+)-inophyllum B and (+)-calanolide A, possible candidates for AIDS drugs. Further examination of the asymmetric IMA with cinchona alkaloids lacking a methoxy group on the quinoline skeleton suggested the influence of the methoxy substituent on stereoselectivity at the stereogenic centers of the chromanone systems.     

Synthesis of di-branched heptasaccharide by one-pot glycosylation using seven independent building blocks

[reaction: see text] We describe an efficient synthesis of di-branched heptasaccharide 1 having phytoalexin elicitor activity in soybeans by one-pot glycosylation. The synthesis involves chemo- and regioselective sequential six-step glycosylations using seven independent building blocks and sequential removal of acyl- and benzyl ether-type protecting groups. The coupling of seven building blocks requires only four chemoselective activitable leaving groups of glycosyl donors. Both the glycosylation and deprotection reactions can be achieved utilizing a parallel manual synthesizer.     

Technical study for SPECT of the head using slant hole collimator

The performance of a 160 keV slant hole collimator (160 keV SH) was compared with that of a 140 keV high resolution collimator (140 keV HR) for SPECT imaging of the head using 99mTc. The minimum radius of revolution was reduced from about 23 cm to 13 cm using 160 keV SH. Relative sensitivity of the 160 keV SH was 108% of that of the 140 keV HR. Compared with SPECT using 140 keV HR, 160 keV SH SPECT yielded approximately a 15% increase in resolution. The 160 keV SH SPECT images of phantom were superior in resolution and contrast to that of 140 keV HR SPECT. We concluded that high quality SPECT images of the head can be obtained from rotating gamma cameras equipped with slant hole collimators.     

Thermolysis of the reaction products from 2-pyridylacetohydrazide and nitrous acid

2,3-Dihydroimidazo[1,5-α]pyridin-3-one (IV) was obtained by thermolysis of 2-pyridylacetyl azide (II) which was prepared from 2-pyridylacetohydrazide (I) on treatment with an equivalent mole of nitrous acid. Treatment of I with excess nitrous acid yielded α-oximino-α:-(2-pyridyl)-acetylazide (V). Thermal decomposition of V gave 3-(2-pyridyl)-1,2,4-4H-oxadiazolin-5-one (VII). 2-Cyanopyridine (IX) was obtained from V by the action of alkali. 2,3-Dihydroimidazo-[1,5-α ]pyridin-3-one (IV) was rearranged to VII upon treatment with nitrous acid. J. Chem. Soc., 14, 993 (1977)     

Steroidal oligoglycosides from Solanum nigrum

Two new steroidal saponins, named nigrumnins I and II, together with two known saponins were obtained from the whole plant of Solanum nigrum L. On the basis of spectroscopic analysis (1H-NMR, 13C-NMR, 1H-1H COSY, TOCSY, HMQC, HMBC and FAB-MS), nigrumnin I was established as (25R)-5alpha-spirostan-3beta-ol 3-O-betaD-xylopyranosyl-(1-->3)-[alpha-L-arabinopyranosyl-(1 -->2)]-beta-D- glucopyranosyl-(1-->4)-[alpha-L-rhamnopyranosyl(1-->2)]-beta-D- galactopyranoside (1), and nigrumnin II was elucidated as (25R)-3beta,17alpha-dihydroxy-5alpha-spirostan-1 2-one 3-O-beta-D-xylopyranosyl-(1-->3)-[alpha-L-arabinopyranosyl-(1--> 2)]-beta-D-glucopyranosyl-(1-->4)-[alpha-L-rhamnopyra- nosyl-(1-->2)l-beta-D-galactopyranoside (2).     

Cobalt-catalyzed Heck-type reaction of alkyl halides with styrenes

A cobalt complex, CoCl2[1,6-bis(diphenylphosphino)hexane], catalyzes an alkylation reaction of styrenes in the presence of Me3SiCH2MgCl in ether to yield beta-alkylstyrenes. A variety of alkyl halides including alkyl chlorides can be employed as an alkyl source. A radical mechanism is strongly suggested for this alkylation reaction.     

Optical switching and alignment of antiferroelectric liquid crystals containing an azo group

The optical properties of two kinds of photochromic antiferroelectric liquid crystal (AFLC) containing an azo group have been examined. Depending on the substituting group at the chiral centre, these AFLCs showed different photoinduced phase transitions by Ar⁺ laser light irradiation. This phase transition has led to a new form of optical switching controlled by a bias voltage. In addition, it was found that these AFLCs caused an azimuthal photoalignment effect regulated by linearly polarized Ar⁺ laser light irradiation. These phenomena were applied to image storage.