The chemistry of terpenes. Part XV. Some oxygenated derivatives of p-menthane
Reaction of (+)-pin-2-ene (1) or (+)-trans-sobrerol (p-menth-6-ene-trans-2,8-diol)(3) with peroxysuccinic acid gives 6,8-epoxy-cis-p-menthane-trans-1,trans-2-diol (5a) and trans-p-menthane-cis-1,trans-2,trans-6,8-tetraol (6). Similarly, pinol (6,8-epoxy-p-menth-1-ene)(7) yields endo-2,endo-6-dihydroxycineol (1,8-epoxy-trans-p-menthane-trans-2,trans-6-diol)(15a) and trans-p-menthane-cis-1,trans-2,cis-6,8-tetraol (16). Hydrolysis of pinol trans-epoxide (trans-1,trans-2:6,8-diepoxy-cis-p-menthane)(12) with water also gives the diol (15a), oxidation of which gives 2,6-dioxocineol (1,8-epoxy-p-menthane-2,6-dione)(17) and endo-2-hydroxy-6-oxocineol (1,8-epoxy-trans-6-hydroxy-p-menthan-2-one)(18a). Borohydride reduction of compound (17) affords exo-2,exo-6-dihydroxycineol (1,8-epoxy-p-menthane-cis-2,cis-6-diol)(19a) and the endo-2-hydroxy-isomer (20a); the hydroxy-ketone (18a) similarly yields only compound (15a).
Treatment of compound (15a) with hydrogen bromide in acetic acid gives mainly trans-2,trans-6-diacetoxy-8-bromo-trans-p-menthane-cis-1-ol (23), which with base affords p-menth-4(8)-ene-trans-1,cis-2,cis-6-triol (22). With hydrogen bromide in acetic acid, compound (5a) gives trans-2,cis-6-diacetoxy-8-bromo-cis-p-menthane trans-1-ol (28) and its 1-epimer (29).
Aqueous mineral acids convert the alcohols (5a) and (16) into trans-p-menthane-cis-1,trans-2,trans-4-cis-6-tetraol (27). The alcohols (6), (15a), and (22) similarly give trans-p-menthane-cis-1,trans-2,trans-4,trans-6-tetraol (24).
Treatment of 2,6-dioxocineol (17) with cold, air-free aqueous sodium hydrogen carbonate gives a mixture of trans- and cis-2,2,6-trimethyl-5-oxotetrahydropyran-3-acetic acids (30; R1= Me; R2= H). In air these are converted into a 6-hydroxyperoxide, which with base affords 2,2-dimethyl-5-oxotetrahydrofuran-3-acetic acid (terpenylic acid)(13a).