Biomedical subjects
Publications and source records attributed to O Tamura.
[structure: see text] The synthesis of (-)-aphanorphine was achieved by using Bu(3)SnH-mediated aryl radical cyclization of 1-benzyloxycarbonyl-2-(2-bromo-4-methoxyphenylmethyl)-2-methoxycarbonyl-4-(phenylthiomethylene)pyrrolidine, leading to exclusive formation of the 6-exo cyclization product.
Factors affecting the stereochemical course of the intramolecular cycloaddition of intermediary alpha-allyloxycarbonylnitrone resulting from transesterification of alpha-methoxycarbonylnitrones 1a-d with chiral allyl alcohols 5 or 6 were investigated systematically. It was found that the factors of diastereofacial selection are highly dependent on the geometries of the allyl alcohols. In the cases where primary or secondary chiral (Z)-allyl alcohols are used, A(1,3)-strain arising from the chiralities in the (Z)-nitrone transition states of the intramolecular cycloaddtion is the most important factor. In contrast, in the case of the reaction using chiral nitrones 1c,d and (E)-allyl alcohols, steric interaction between the chiral N-substituent and the trans substituent of the olefin moiety in the intermediate is dominant. These aspects were applied to geometry-differentiated cycloaddition using a mixture of (E)-5 and (Z)-5. As a typical example, treatment of bulky 1b with a 1:1 mixture of (E)-5 and (Z)-5 in the presence of a catalytic amount of TiCl(4) and MS 4A gave 7b as the predominant product among four possible products.
Bu(3)SnH-mediated aryl radical cyclization onto methylenecycloalkanes having a phenylthio, an ester, or a nitrile group at the terminus of the alkenic bond provides exclusively exo cyclization products. The results are in sharp contrast to those reported for nonsubstituted methylenecycloalkanes, which give exclusively endo cyclization products. Formation of endo cyclization products has been suggested to be a result of a consecutive 5-exo cyclization of an aryl radical and neophyl rearrangement. The exo-selective aryl radical cyclization offers a new method for synthesizing fused aromatic compounds containing a benzylic quaternary carbon atom.
Optically pure (5R)- [and (5S)]-5,6-dihydro-5-phenyl-2H-1, 4-oxazin-2-one N-oxides [(5R)- and (5S)-2] were designed as chiral (E)-geometry-fixed alpha-alkoxycarbonylnitrones 1. The nitrones (5R)- and (5S)-2 were synthesized by three-step oxidation of (R)- and (S)-phenylglycinols [(R)- and (S)-3], condensation of the resulting (R)- and (S)-2-hydroxylamino-2-phenylethanols [(R)- and (S)-5] with glyoxylic acid, and cyclization of the intermediary nitrones (R)- and (S)-6b. The nitrone (5R)-2reacted with olefins 7-14 under mild conditions to afford the corresponding cycloadducts 15-22 as the main products via the least sterically demanding exo modes. Cycloadduct 30 obtained from (5S)-2 and cyclopentadiene was effectively elaborated to (1S,4S, 5R)-4-benzyloxycarbonylamino-2-oxabicyclo[3.3.0]oct-7-en-3-one (28), the key synthetic intermediate of carbocyclic polyoxin C.
Explore the source record for details and available documents.
Tests of K(+)-sensitive microelectrodes were made using a plastic chamber, which consisted of upper and lower compartments separated by a partition with a small opening in the center. After the upper and lower compartments were filled with 25 and 100 mM KCl respectively, the tip of a K(+)-sensitive electrode was moved up and down through the partition opening, while recording potential changes. Some hydrodynamic events associated with electrode movement and effects of gravity upon spherical diffusion are discussed.
We studied the binding characteristics of anti-acetylcholine receptor antibody (AChR Ab) in sera of nine patients with myasthenia gravis (MG) using affinity-purified extraocular muscles (EOM) and foot muscles (FM) of bovine species. The titer of AChR Ab measured with EOM was the same as that measured with FM for both ocular and generalized MG. In patients with ocular MG, the affinity of AChR Ab, determined by Scatchard analysis, was higher for FM than for EOM (P less than 0.05), whereas it was the same for EOM and FM in those with generalized MG. On the other hand, the affinity of AChR Ab for FM was lower in generalized MG than in ocular MG (P less than 0.05), but that for EOM did not differ between the two types of MG. The affinity of AChR Ab did not change after passing the patients' sera through an EOM-affinity column. The EOM-affinity column treatment of the sera decreased the AChR Ab titer measured with EOM in all patients, but the AChR Ab titer measured with FM was decreased in only some of the patients. These data indicate that there are polyclonal or heterogeneous AChR Abs in the sera of MG patients, which does not help to explain the clinical difference between ocular and generalized MG.
Prifinium bromide was administered for eight weeks to three patients with exotropia. Under general anaesthesia active discharges from the lateral rectus muscles were demonstrated by electromyography. When a slight adductive force was applied to the straight or the master eye, active discharge from the lateral rectus of the associate eye disappeared in all patients, and this eye moved in the direction of orthophorisation. The discharge reappeared when the master eye was released from the forced adduction. From these results the authors concluded that proprioception is involved in the magician's forceps phenomenon discovered by Mitsui in exotropic patients in 1978.
Clinical studies were carried out during digoxin maintenance therapy to clarify three questions concerning digitalis therapy: optimal time for blood sample collection for serum digoxin concentration (SDC), the overlapping range of SDC levels in which some patients may be intoxicated while others are not, and both resistance and sensitivity of atrial fibrillation (AF) to digitalis. The SDC curve after a single dose of digoxin or beta-methyldigoxin shows the appropriate sampling time to be at least 12 hours after the administration. The optimal time is 24 hours. The overlapping SDC range was 1.7-2.7 ng/ml. There were significant differences in CTR and ventricular rates in AF between intoxicated and non-intoxicated groups. This suggests that susceptibility to digitalis increases with the severity of underlying heart disease. Precipitating factors such as CTR should be taken into consideration, if the SDC is in the overlapping level. Digitalis resistance occurs in 6.7% of 105 patients with AF, and more frequently in hypertensive heart disease than others. Digitalis sensitivity occurs more often in the elderly and in patients with dilated cardiomyopathy. But it is not necessary to attain higher therapeutic levels for AF than for sinus rhythm. Clearly optimal digitalis therapy for AF can be best accomplished when precise clinical findings, SDC and EKG recordings are carefully monitored and used to correct treatment.
Explore the source record for details and available documents.
The unusual phenomenon of reverse phase reflex eye movement was first described by Ishikawa. In this study the reflex frequency response was examined by electrooculography. In typical cases a reflex was observed by repeated forced duction up to 9 Hz. As a result it was postulated that proprioception is usually involved in reverse phase reflex eye movement, because visual eye movement cannot respond to a movement beyond 1 Hz. When the lag-times between the peaks of forced duction in one eye and those of the reflex movement in the other were measured, they were almost zero or even negative at high frequencies of forced duction as 6 and 9 Hz. This phase advance of the reflex movement was explained only when the receptor of the reflex had a dynamic response, because 90 degrees phase advance results in a reflex through such a receptor. The primary ending of muscle spindle represents such a receptor. The magician's forceps phenomenon as first discovered by Mitsui in exotropia is supposed to be a blocking reflex through the tendon organ. The transmission lag-times of both reflexes can be as short as 20 msec, but must be slightly longer to consider them to be monosynaptic.
An infant girl manifesting bilateral cryptophthalmos with multiple associated malformations was followed from birth. The globes were almost covered by a fold of skin and the findings were interesting in regard to the etiology of cryptophthalmos. The other congenital deformities included scaphocephaly, somewhat low-set ears, accessory tragi, a high arched palate, and funnel chest. The child was operated on at the age of 4 months with relatively satisfactory results, although she died suddenly of acute heart failure 4 months postoperatively.
The level of ascorbate in the aqueous humor and surrounding intraocular structures in enucleated arterially perfused rabbit eye was investigated. The enucleated eye preparation was shown to be capable of secreting ascorbate from the perfusate into the aqueous humor. Ascorbate in the iris, ciliary body and cornea was released into the aqueous humor when the eye was perfused with ascorbate-free solution. Failure to obtain aqueous flow rates from the decay of ascorbate in the anterior chamber was due to the contribution of ascorbate from these ocular tissues during the perfusion. Histochemically, ascorbate was localized in the pigmented epithelial layer in the valleys between the ciliary processes and the pars plana of the ciliary body and in the iris. In the cornea, distinct localization of ascorbate was observed in the endothelium and basal cell layer of the epithelium.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.