Dioxa-isotwistanes

which in aqu. NaCl-solution was transformed into the chloromercuri compound 

10° -iodo-2,7-dioxa-isotwistanes 125 and 127), whose composition depended on the applied reaction conditions In all of the above reactions the yields were very high, e.g. the overall yield of 119 120 122 125 + 127 was 85%. The 10 - 

7-Dioxa-isotwistane 128) was prepared by intramolecular substitution at C(7) of endo-2-hydroxy-exo-7-tosyloxy-9-oxabicyclo[3.3.1 ]nonane 129) in methanolic KOH-solution in 62% yield. 

Treatment of the tetrahydropyranylether 130 with methanesulfonic acid in methanol yielded beside 26% of the corresponding alcohol 131,45% of l-methoxy-2,7-dioxa- 

As already mentioned in 2.1.2.3., boiling a solution of the anti-diepoxide 21 in 0.5N HCl gave a mixture of 4 l0 -dihydroxy-2,7-dioxa-isotwistane (22) and ada-mantane-diol 13. Both diols were also characterized as their acetates 25 and respectively. 

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Base-hydrolysis of the. lO -acetoxy-isotwistane 246 (3.2.3.) yielded the corresponding alcohol 137, which was also characterized as its tosylate 267 (3.2.3.). The azide 287 (3.2.3.) was catalytically reduced (H2/raney-nickel) to the 10° -amino-iso-twistane 330. Oxidation of the isotwistanol 137 with Jones-reagent gave the ketone 331, which was transformed via desulfuration with raney-nickel of the corresponding thioketal 332 to unsubstituted 2,7-dioxa-isotwistane 128, see also 2.2.2.1.). 

Base-hydrolysis of the 10° -acetoxy-isotwistane 310 (3.4.3.) gave the alcohol 333, which was also obtained as sole product in a 99% yield by L1A1H4-reduction of the ketone 331. LiAlH4-treatment of the tosylate 334, prepared from the alcohol 310, yielded only alcohol 310 again and no unsubstituted 2,7-dioxa-isotwistane 128). Obviously the cleavage of the bond between 0-C(10)° and S—OC(10)° is preferred over the formation of an oxonium ion G 59. This result, compared with the exclusive formation of an oxonium ion G 46 (no reaction to the alcohol 137) in the analogous treatment of the 10° -tosylate 267 (3.2.3.), is a qualitative measure for the differences of the tendencies for the formation of the oxonium ions G 46 and G 59, starting from C(10)° - and C( 10)° -substituted isotwistanes ... 

Optically Active 2,7-dioxa-isotwistane, -twistane and -twista-4,9-diene ... 

The subsequently applied synthetic scheme was analogous to the one for the corresponding racemic compounds (see 2.2.2.I., 3.2.3. and 3.2.4.). Treatment of the (—)-alcohol 379 with iodine in chloroform yielded the (-)-10° -iodide 383 as sole product. Its reaction with silver tosylate in acetonitrile led to a mixture of 10°(7).tosyloxy-isotwistane 384 and -twistane 386, which was directly treated with LiAlH4 in refluxing dioxane to give a mixture, easily separable by vpc., of (—)-2,7-dioxa-isotwistane 385 [oc]d = —23.3 0.7°) and (-)-2,7-dioxa-twistane 387, see Table 8). The absolute configuration of 387 [(—)-( R, 3R, 6R, 8R), right-handed helix (P)] and of all other compounds involved in its synthesis was determined by chemical correlation with (—)-(2S)-malic acid (559). As relais compounds served the endo-2-hydroxy-9-oxabicyclo[3.3.1]nonanes +)-390 and (—)-J97, (-t)-5-hydroxy-cyclooct-l-ene [ +)-392] and the 4-methoxy-suberic acid dimethylester —) 393 and +)-394. 

Between approx. 1200 and 800 cm all dihetero-tricyclodecanes show marked sharp absorption bands. Comparing, e.g. the spectra of unsubstituted skeletal isomers, already gives good hints for the assignment of a certain structure type because compounds of higher symmetry exhibit less absorption bands than those of lower syih-metry [e.g. 2,7-dioxa-twistane 212) and 2,7-dioxa-isotwistane 128), resp.]. 

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