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Silylation of cellulose
(1977)
Ethane-l:2-diol and propane-l:3-diol reaet with 1: 1:3:3-tetramethyl-l:3-dichlorodisiloxane forming the corresponding rings. However, no ring compounds could be traced tbrough the reaction between butane-l :4-diol, glycerol and the dichlorodisiloxane respectively, where only polymeric compounds are formed. The silylation products of the di- and trihydroxy alcohols, as model compounds, has confirmed that the ring formation during silylation of cellulose with dichlorodisiloxane is uncertain.
15 new C/Si-analogue pairs (C-compounds and sila- or disila-substituted derivatives, respectively), which are structurally related to nifedipine, have been synthesized. These and some further C/Si-pairs have been investigated comparatively with respect to their physicochemical and pharmacological properties. Using reversed-phase thin-layer chromatography it was shown that both the sila- and disila-analogues are more Iipophilic than the corresponding C-compounds. With respect to the in vitra spasmolytic potencies the Si-compounds show approximately similar structure-activity relationships to their carba-analogues. However, in some cases marked differences in in vivo effects (cardiovascular and antihypertensive activity) could be demonstrated.
The crystal structures of the (R)-enantiomer (2b) and the racemate (1 b) of (cyclohexyl)phenyl[2- (pyrrolidin-1-yl)ethyl]silanol (sila--procyclidine) have been determined by X -ray structural analysis. The absolute configuration of (2b) was established. (2b) crystallizes in the orthorhombic space group P2\(_1\)2\(_1\)2\(_1\), with a = 15.221 (1 ), b = 17.967(1 ), c = 6.463(1) A, and Z = 4. (1 b) crystallizes in the monoclinic space group P2\(_1\)/c, with a = 6.441 (1 ), b = 17.1 82(7), c = 16.707(4) A, ß = 1 03.86(2r, and Z = 4. The structures were refined to respective R factors of 0.044 and 0.058. The molecular conformation of sila-procyclidine is identical in the two different structures. lntermolecular 0-H • • • N hydrogen bonding is observed in both crystallattices.ln (1 b) (R)- and (S)-configurated molecules form centrosymmetric dimers, in (2b) the (R)-configurated molecules are linked into infinite chains parallel to the c axis. The (R)-configurated sila--procyclidine (2b) has higher affinity for ileal and atrial muscarinic receptors of the guinea pig than the (S)-configurated enantiomer (3b).
Enantioselective reduction of acetyldimethylphenylsilane by Trigonopsis variabilis (DSM 70714)
(1987)
Growing and resting cells of the yeast Trigonapsis variabilis (DSM 70714) can be used for the enantioselective reduction of the organosilicon compound acetyldimethylphenylsilane (J) to give optically active (R)-(1-hydroxyethyl)dimethylphenylsilane [(R)-2] in good yields. The enantiomeric purity of the isolated product was determined tobe 62-86% ee depending on the substrate concentration used. Both substrate and product caused an inhibition of the reaction at concentrations higher than 0.35 and 0.5 g/1, respectively. Besides, higher substrate and product concentrations led to increased formation of the by-product 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane. Considering the limiting substrate and product concentrations, it was possible to use the same biomass at least 5 times without significant loss of enzyme activity. 3-Methyl-3-phenyl-2-butanone (5) and acetyldimethylphenylgermane (7), which represent carbon and germanium analogues of 1, were also found to be accepted as substrates by Trigonapsis variabilis (DSM 70714). The reduction rates of the silicon {1) and germanium compound {7) were much higher than the transformation rate of the corresponding carbon analogue 5.
Thirty strains of microorganisms (bacteria, yeasts, fungi and green algae) were tested as resting free cells for their ability to transform acetyldimethylphenylsilane (1) enantioselectively into (R)-(1-hydroxyethyl) dimethylphenylsilane [(R)-2]. The biotransformations were monitared by GC (packed OV-17 column), and the enantiomeric purities of the products isolated were determined by HPLC (cellulose triacetate column, UV detection). All microorganisms tested were found to reduce 1 enantioselectively to give (R)-2. Under the test conditions used, the yeast Trigonapsis variabilis (DSM 70714) was found to 1 exhibif the highest specific activity (1.5 mg product x g cell wet mass\(^{-1}\) x min\(^{-1}\) ), whereas the highest enantioselectivities were observed for the bacteria Acinetobacter ca lcoaceticus (ATCC 31012) (>95% ee), Brevfbacterium species (ATCC 21860) (90% ee) and Corynebacterium dioxydans (ATCC 21766) (>95% ee), the yeast Candida humico la (OSM 70067) (90% ee), the fungus Cunninghame lla e legans (ATCC 26269) (94% ee), as well as the cyanobacterium Synechococcus leopoliensis (94% ee).· From the green algae tested, Chlamydomonas reinhardii showed the highest.enantioselectivity (85% ee).
The present study was designed to further charaeterize the presynaptie musearlnie M\(_1\)-reeeptor responsible for the inhibition of neuragenie eontraetions in the isolated rabbit vas deferens. Eleetrically induced twiteh eontraetions of this preparation were inhibited by the M\(_1\)-agonist, MeN-A-343, and by some of its analogs: 4-ehloro-phenyl derivative> MeN-A-343 > trans-olefinie analog> cis-olefinie analog. The same rank order of potency was observed for these agonists to raise the blood pressure of pithed rats by stimulation of M\(_1\)-receptors in sympathetie ganglia. A highly signifieant eorrelation was found between the antimusearinie potencies of atropine, pirenzepine and a series of 9 antagonists strueturally related to the ganglionie M\(_{1\beta}\)-receptor selective compounds, hexocyclium and hexahydro-difenidol, to antagonize the MeN-A-343-indueed inhibition of twitch eontraetions in rabbit vas deferens or the musearine-indueed depolarization in rat isolated superior eerVieal ganglia. It is suggested that the presynaptie musearlnie receptor that mediates inhibition of neuragenie contraetions in rabbit vas deferens is of the ganglionic M\(_{1\beta}\)-type.
The synthesis of the potent and highly selective silicon-containing antimuscarinic agent o-methoxysila- hexocyclium methyl sulfate and its corresponding tertiary amine (isolated as the dihydrochloride) is described. The quarternary compound is an omethoxy derivative of sila-hexocyclium methyl sulfate, which represents one of the tools currently used in experimental pharmacology for the subclassification of muscarinic receptors. The omethoxy derivative, the pharmacological profile of which differs substantially from tbat of the nonmethoxy compound, is also recommended as a tool for the investigation of muscarinic receptor heterogeneity.