Oxa-7-thia-isotwistanes

Acid-catalyzed intramolecular addition of the free HS-group of the mercaptane 177 to the double bond C(6)-C(7) yielded almost quantitatively the tricyclic compound 179. Treatment of it with HCl/ethanol gave the corresponding ketal 180, with thio-nylchloride the two isomeric chlorides 181 (isotwistane-derivative) and 184 (bicyclo- 

Using an analogous starting material, the bieyclic mercaptane 178 reacted with bromine in carbontetrachloride at —18° yielding approx. 95% of lO -bromo-2-thia-7-oxa-isotwistane 183) .  

Oxymercuration (mercuric acetate) of endo-7-hydroxy-9-thiabicyclo[4.2.1]non-2-ene (188), a starting material prepared by the synthesis 185 - 186 187 - 188 from 

A further derivative, the 9° -bromo-2-thia-7-oxa-isotwistane 191), was obtained by reaction of endo-2-mercapto-9-oxabicyclo[3.3.1]non-7-cne (790) with bromine. 

Intramolecular substitution of the exo-3-tosyloxy group by the endo-7-hydroxy group in 195 opened a further access to unsubstituted 2-thia-7-oxa-isotwistane 182). The starting material 195 was obtained by NaBH4-reduction of 185 - 192 + 193) 

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An analogous result was obtained with the corresponding 10 -tosyloxy-2-thia-7-oxa-isotwistane 1343), see 4.3.4. 

Some 10-substituted 2-oxa-7-thia-isotwistanes were oxidized with one equivdent of hydrogen peroxide in acetic acid for chemical correlations. In each case stereo-j specifically only one of the two possible S(7)-epimeric sulfoxides was formed. 

The 10 -acetate 248 and 10 -iodide 147 gave the corresponding sulfoxides 250 and 164 with S(7) -configuration whereas the 10 -alcohol 335 and the 10SC )-iodomercuri compound 144 led to the sulfoxides 337 (also characterized as its acetate 338) and 155 with S(7) -configuration On the other hand, oxidation of the sterically unhindered lO -acetate 312 as well as of the unsubstituted 2-oxa-7-thia-isotwistane 148) yielded the sulfoxides 339 and 340 also with S(7) -configuration ... 

Oxa-7-thia-isotwistane [148), 10 -Hydroxy-2-oxa-7-thia-isotwistane 335) and 10 -Acetoxy-2-oxa-7-thia-twistane 249)... 

Treatment of unsubstituted 2-oxa-7-thia-isotwistane 148 2.2.3.1.) with raney-nipkel, yielded 74% of 9-oxabicyclo[4.2.1]nonane 408) and reductive desulfuration of the alcohol 335 (4.3.2.) 85% of endo-2-hydroxy-9-oxabicyclo[4.2.1 ]nonane (409) Analogous reaction of the 10 -acetoxy-twistane 249 (3.2.3.) with raney-nickelj however, led to endo-2-acetoxy-9-oxabicyclo[3.3.1]nonane (47( ) ... 

Oxa-7-thia-isotwistanes as Well as Corresponding Sulfoxides and Sulfongs. Applying the results of extenave studies (using the NMR-method) of the anisotropic effects in sulfoxides by Foster et (see also the NMR-sepctra of 2-oxa-... 

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