A sample of [³H] tobrarnycin (, 000 Ci/Mole) has been synthetized and incubated with
the bacterial ribosome and its subunits. The results obtained show that this antibiotic has
two types of binding sites. The primary one is probably responsible for the inhibition of
protein synthesis whereas the secondary one is probably related to the misreading and reading
tiirough of the messenger RNA.

抄録全体を表示

The activities of tobramycin derivatives acetylated and ethylated on the '-N, 2'-N and 3-N positions were examined. The MICs of these derivatives against tobramycin sensitive strains indicated that 2'-N-ethylated and '-N-ethylated derivatives have a fairly good activity, and confirmed that the 3-N position is the most important one for antibiotic activity since 3-N derivatives were less active. The MICs of these derivatives against tobramycin resistant strains, and their inactivation by tobramycin modifying enzymes were examined. These results showed that 2'-N or '-N ethylation protects the drug against inactivation by AAC(2') or AAC('), respectively, and 2'-N-ethyltobramycin and '-N-ethyltobramycin were active against strains containing these modifying enzymes. On the other hand, 3-N ethylation protects the drug against inactivation by AAC(3) but 3-N-ethyl tobramycin does not inhibit strains containing this enzyme.

抄録全体を表示

Circuit techniques to enhance the linearity of input-voltage-to-current (V/I) conversion and to increase the output impedance of a current source by compensating for the low intrinsic gain of a transistor were introduced to realize a high-frequency operational transconductance amplifier (OTA) for a low supply voltage using sub-100-nm CMOS processes. Applying these techniques, a MOS th-order Gm- linear-phase low-pass filter (LPF) was realized using a 65nm CMOS process. A simplified biquad LPF that can serve as a component of a th-order LPF was newly developed by replacing OTAs with resistors. As a result, the -3dB frequency bandwidth, group delay ripple, 3rd-order distortion, and 3rd-order input intercept point (IIP3) were 200MHz, 2.2%, ≤ -55dB with a 100MHz input, and +10.3dBm, respectively, all with a ±0.1Vp-p input signal at each input terminal in the pseudodifferential configuration. The LPF including an output buffer dissipated 60mW in the case of a 1.2V supply. Wide spurious-free dynamic range (SFDR) characteristics were confirmed up to high frequencies.

抄録全体を表示

(³H) Tobramycin was used as a probe to determine the relationship between the structure of aminoglycoside antibiotics and their ability to remove this drug from its higher affinity binding site on the ribosome. The dissacharide moieties (neamine, tobramine, gentamine) appeared to have a common binding site, whereas the kanosamine, garosamine and ribose moieties determined the specificity of this binding. Amikacin and butikacin behaved in an anomalous manner in spite of their close structural relationship to tobramycin.

抄録全体を表示

Repetitive liquefactions in angular and subangular gravels from an alluvial fan, in the case of two earthquakes with accelerations lower than that of a former which had caused liquefaction some months before, are described. The liquefaction took place from the surface, down to a depth of approximately 10 m. Water laden with sediments spouted out for some tens of minutes after the strong motion ceased. Knowledge of the grain size distribution of the sediments inside the body of the alluvial fan roughly defines the areas of the fan prone to future liquefaction. Non-repetitive liquefaction in overconsolidated fine fluvio-lacustrine sand of glacial origin at the unusual depth of 14 m to 16 m is also described. From the observation of sand lifted up for 10 m inside a large diameter well, and of that which spouted out from several microvents, it was estimated that extra-pore pressure was close to lithostatic conditions. Nevertheless, modeling of intrinsic pore pressure buildup on the DESRA2 programme gives lower values than the experimental one. Geotechnical characteristics of the 12 m-thick sandy stratum indicate that the upper part is unusually soft, either due to water circulation or past repetitive liquefactions which prevented reconsolidation. It is suggested that excess pore pressure generated by the earthquake was also due to redistribution of pressure from adjacent sediments.

抄録全体を表示

Agaricus blazei is an important fungus for producing bioactive compounds. There are some reports of polysaccharides and steroid derivatives from the fruiting bodies of A. blazei. However, the chemical examination of the secondary metabolites of the cultured mycelia of this species has not been reported. Eight compounds, an unprecedented skeleton have been isolated from the cultured mycelia of A. blazei. The structures of the novel compounds each named blazeispirols A (1), (2), (3), D (), () X(), Y () and Z () were confirmed by extensive 1D and 2D NMR spectral data and X-ray analysis. Blazeispirols A (1), (2), (3), D () and () were des-A-ergostane type compounds having spiroacetal structure as a side chain. Blazeispirols X () and Y () were determined to be (20S, S, 23R, 24S)-1 (10→) abeo-14β, :, 25-diepoxyergosta-,,,11-tetraene-3α,23-diol and (20S, S, 23R, 24S)-14β,:,25-diepoxy-,23-dihydroxyergosta-,,11-triene-3,-dione by comparison of extensive 1D and 2D NMR spectral data with that of blazeispirol A. The biosynthesis of blazeispirol A was investigated by feeding ^<13>-labeled acetates and methionine to the growing cultures of A. blazei. The labeling patterns of 1 derived from singly and doubly ^<13>-labeled acetates were consistent with that of ergosterol reported previously except for the A-ring and then ^<14>-labeled ergosterol was incorporated into blazeispirol A. Taking the structures of blazeispirols Z and D into consideration, it can be assumed that blazeispirol A is biosynthesized from ergosterol by the cleavage of -, - and -1, -10 bonds on retro aldol condensation and Michael reaction via such as intermediate A as shown in Fig. . A large number of ergostane-type steroids have been isolated from many fungi. However, blazeispirol A is the first example of a naturally occurring des-A-ergostane-type steroid including a spiroacetal structure moiety as a side chain.

抄録全体を表示

Two new partially saturated tricyclic ring systems, , a, , , , 10, 10a, 11-octahydro-11-oxodibenz [, ] oxepins (3a and 3), and -thiepins (a and ) were synthesized. Compounds a and were desulfurized to give a pair of isomeric 2-methylbenzoylcyclohexanes (10a and 10). Deuterated a and (11a and 11) were prepared starting from butadiene- (12). The stereochemical features of 3a (trans), 3 (cis), a (trans) and (cis) are compared with those of 10a, 10, 11a and 11 on the basis of proton nuclear magnetic resonance data.

抄録全体を表示

Nine isoquinoline alkaloids belonging to the protoberberine, proaporphine and bisbenzyl-isoquinoline series were isolated from Caryomene olivascens (Menispermaceae). Four compounds are new : (-)-2-norlimacine (), (-)-caryolivine (), (+)-1, 2-dehydro-2-norlimacusine () and N-formylstepharine (3). The last one is the first N-formyl derivative to be reported in the proaporphine group. Its biogenetic origin is discussed. Structures were established on the basis of 360 MHz (FT) nuclear magnetic resonance measurements and also by chemical correlation in the case of 3.

抄録全体を表示

11-Amino-, a, , , , 10, 10a, 11-octahydrodibebenzo[, ]thiepines (a-d) and -oxepines (a-d) were synthesized by the Leuckart reaction of , a, , , , 10, 10a, 11-octahydro-11-oxodibenzo[, ]thiepines (1a, )and -oxepines (2a, ) followed by hydrolysis of the reaction products a-d and a-d, respectively. The four diastereomers, cis(a-H, 10a-H)-cis(10a-H, 11-H) a and a, cis(a-H, 10a-H)-trans(10a-H, 11-H) and , trans(a-H, 10a-H)-trans(10a-H, 11a-H) and , and trans(a-H, 10a-H)-cis(10a-H, 11-H) d and d, were isolated and their configurations and conformations were elucidated by chemical methods together with ¹H-nuclear magnetic resonance spectroscopic and X-ray crystallographic analyses.

抄録全体を表示

Examination of the secreted wax of a scale insect, Ceroplastes ceriferus has shown the presence of various compounds of considerable biogenetic interest. (a) The sesquiterpenes were enantiomeric with respect to those from . rubens, which infests the same host tree. Each insect may possess a specific set of - cyclases for the formation of sesquiterpenes. () Among the identified twelve diterpenes, two of labdane skeletons were the first naturally occurring compounds. () The sesterterpenes (1-)(-10) having 14-membered monocyclic skeletons were the first naturally occurring compounds being independent of the host tree. Remarkable is the finding of sesterterpenes resulting from different biogenetic cyclization mode from the same species, collected in different districts, or from the different species of the same genus. (d) The "cyclic" wax were the esters consisting of fatty acids (_<10>-_<32>) and unusual cyclic alcohols (diterpenes and sesterterpenes). Structures and stereochemistry of nine new sesterterpenes will be discussed on the basis of spectroscopic and chemical methods: Cericerol-I (1), cericerol-II (2), 13-methoxy cericerene (3), 13-ethoxy cericerene (), α-cericerol-I (), cericeroic acid (), 18-dihydro-19-ol cericeroic acid (), cericera-2(),(Z),10(),15(), 18-pentene-25-acid (), cericera-2(),(Z),10(),15(), 18-pentene-24-acid (), and cericerene-15,24-diol (10). Possibility of the configurational isomers for the structures ()and () at the position -24 and -25 are still remained to be elucidated. Bridged hydrocarbon (16) which was obtained by acid treatment of tosylate of cericerol-I (1) indicated the crown shape (A) for (1).

抄録全体を表示

Five new marine _<29> sterols (2-) were isolated from the soft coral Sinular ia mayi of the Ishigaki Island, Okinawa. The Spectrosocpic data showed that they are the polyhydroxy derivative of sarcosterol (1), a marine sterol having a unique 23-methyl and a 17(20)-double bond. Sterol 2 was the 25-monohydroxy derivative of 1. The NOE experiment of its 25, 26-didehydro derivative indicated that the stereochemistry at -23 and 24 was identical with that of peridinosterol, whose absolute configuration has previously been established. Sterol 3 was the 25,26-dihydroxy derivative of 1. It was converted to 2 by reductive cleavage of the -26 tosyloxy bond by LAH. Sterols and were shown, by spectroscopic analyses, to be , 25-dihydroxy and ,23,25-trihydroxy derivatives of 1. The stereochemistry in the side chain was derived from interpretation of the coupling pattern and the results obtained by NOE experiments. On storage sterol was found to be converted, by dehydration, to sterol having a tetrahydrofuran ring on the side chain Two new cembranoids sinulariol () and mayolide (), simultaenously isolated from S. mayi, were correlated to the known compounds sinulariol A () and mayolide (10) by dehydration. The pyridine-induced deshielding effects, observed in the ^1H NMR spectra of and 10-12, indicated that the absolute configuration at - of to be (R) and that of 10-12 to be (S). A new polyhydroxygorgostane (15) was obtained from the Andaman Sea soft coral Lobophytum strictum. The structure was derived, by spectroscopic data. to be 1β-hydroxy--deoxy derivative of the known compound andamansterol.

抄録全体を表示