Organosilicon compounds III. Silicon‐substituted thiophene derivatives of mercaptoethylamine as possible radioprotective agents

Abstract

The preparation of the first organosilicon containing derivatives of mercaptoethylamine as possible radioprotective agents is described. The synthesis of these compounds via the thiazolidine intermediate was chosen due to the known radioprotective action of certain thiazolidines. We have prepared seventeen previously unreported organosilicon derivatives of which eleven contain the thiazolidine moiety and six are derivatives of mercaptoethylamine. The ability of these derivatives to protect against ionizing radiation will be determined.The synthesis and evaluation of silicon-substituted medicinal agents is rapidly developing into an exciting and potentially explosive area of medicinal chemistry. TheThe apparent potential of organosilicon medicinals coupled with the known radioprotective action of 2-aminoethanethiol has prompted us to synthesize silicon substisimilarities, as well as the differences, between organo-carbon and organo-silicon compounds suggests that organosilicon containing medicinals would show unique physiological properties.considers that silicon, although larger than carbon, pos-Si-C bond length is approximately 20% longer than the C-C bond. Furthermore, silicon has a lower electronegativity (en = 1.8) than carbon (en = 2.5), and it is able to utilize its 3d-orbitals for bond formation. This concept appears particularly attractive when one 0 -R e ($i.Rl n -B u L i ___, sesses covalent bonding characteristics ( s p 3 ) and that the -R gThat organosilicons can function as medicinals was confirmed by Fessenden and Coon, who prep'ared organosilicons that exhibited muscle relaxant and tranquilizing properties (2,3).The marked lipid solubility of silicon ethers has been successfully established by Chang and Jain (4), who prepared several testosteroxysilanes and determined the effectivenessof these drugs. Similarly, Brown and Laos (5) have prepared a number of steroidal oxysilanes and have found these to have anabolic and androgenic activity. Ghoby and Neuworth (6) have prepared trimethylsilyl derivatives of salicylic acid while Gertner, Rosen and Zilkha (7) as well as Ruehlmann, Hils and Graubaum (8) have prepared organosilicon derivatives of aminoacids. Frankel and coworkers (9) have synthesized several silicon containing barbiturates, a silicon containing analogue of chloroamphenicol, and phenethylamine having a trimethylsilyl moiety attached to the aromatic grouping. Leasure and Speier synthesized a group of (haloalkyl) silicon compounds which were found to have strong herbicidal activity and in mme cases to act as defolients (10). SCHEME A SCHEME 8 n L J I

Organosilicon Derivatives of Sulfur

“…Investigation of the addition of organosilicon thiols to organosilicon vinyl sulfides led to the discovery of the isomerization of organosilicon thioacetals (mercaptals) to symmetrical ethers of l,2-ethanedithiol, which proceeds both in the presence of peroxides and without them, even during distillation in vacuum [1231: In this way it was possible to obtain good yields (60-80%) of 2-thienylsilanes [61,183,268,350,356,879,968], 2-benzothienylsilanes [289,486,670], and 1-,2-,3-, and 4-dibenzothienylsilanes [289,357,361,392,486,670]. It was not possible to synthesize N-triphenylsilylphenothiazine by the reaction of N-phenothiazinyllithium with triphenylchlorosilane indiethyl ether (18 h at room temperature) [352], while the yield of I-thianthrenyltriphenylsilane in the reaction of I-thianthrenyllithium with triphenylchlorosilane is only 9.5% [360].…”