@article{b8325a4609de4f08b92bc406e98b8a84,
title = "Terpenoid chirons: Preparation and transformations of 2-hydroxy-1,1,4a(R),6-tetramethyl-trans-Δ5,6-octalin",
abstract = "Octalins 4 and 5 are prepared conveniently in 3 steps from commercial 18β-glycyrrhetinic acid and converted to a variety of functionalized trans-AB ring chirons.",
keywords = "glycyrrhetinic acid, octahydronaphthalene, retro-Diels-Alder, steroid, thermolysis",
author = "Falck, {J R} and Sukumar Manna and S. Chandrasekhar and L. Alcaraz and C. Mioskowski",
note = "Funding Information: readily reanauged to allylic alcohol 9 upon exposure to BF3*Et20 at 0%. Interestingly,t he interactiono f 8 with a Bronsted acid, camphwsulfonic acid. resulted in a 1:2 mixture of 9 and 13. Mild oxidation of 9 afforded enone 10, mp 123-125%; its regioisomer1 1 was securedb y dii oxidation of 6 with pyridinium dichmma@& butyl hydmpemxide.1H0 ydroborationo f 7 was relatively sluggish,p resumablyd ue to steric hindrancea boutt he tetra-substitutedo lefii. Subsequento xidation led to ketone 12 as a 73 mixture of methyl isomers iu modest overall yield As anticipated, reaction of 6 with singlet oxygens moothlyg eneratede xocyclic allylic alcohol 13. Accesstotheuan&sed 6,5-bicycle 14 followed from ozonolysis of 6 and aldol condensationo f the -Itant keto-aldehydeU. sing RhCl,.*t 6 could be isomerized to a 4:l equilibrium mixture favoring Ae7-olefin 15. In cons&ration of their ease of preparation, cost, and differentially functional&d rings, we anticipate these& irons will find many applicationsin terptnet otal synthe~is.~~ Acknowledgement: Supported financially by the USPHS NM (GM31278). the Robert A. Welch Foundation and the CNRS. Reference and {\textquoteleft}Notes 1. For nzcent, pertinent examples containing the 1,1,4a-trans-nimethylhydronaphalenmeo iety see,F orskolin (adenylatec yclase stimulant): Colombo, M.I.; Zinczuk. J.; RDveda, E.A. Terrohadron 1992.48, 963-1037. K-76 (complement inhibitor): Corey, E.J.; Das, J. J. Am. Chem. Sot. 1982, 104, 5551. Warburganal (insert antifeedant): de Groot, A.; van Beek, T.A. Rec. Trav. Chim. 1987,106. 1-18. Stypoldione (anticancer,i chthyotoxic): Mori, K.; Koga, Y. Bioorg. Med. Chem. L&t. 1992,2,391-394. Taxodione (anticancer): Engler, T.A.; Sampath, U.; Naganathan, S.; Velde, D.V.; Takusagawa, F.; Yohannes, D. J. Org. Chem. 1989.54.5712-5727. Stellifedus (anticancer):T suda, M.; Ishibashi, M.; Agemi, K.; Sasaki. T.; Kobayashi, J. Tetrahedron 1991.47, 2181-2194. Baiyunoside (sweetener): Yamada, H.; Nishizawa, M. ibid. 1992,48, 3021-3044. Ambrox@ (perfume component): B&hi, G.; Wiiest, H. ffelv. Chim. Acta. 1989.72, 996. Recent reviews: Fraga, B.M. Nat. Prod. Reports 1993.397-419. Hanson, J-R. ibid. 1993, 159-174. precedingp aper in this series on chiral precursorsv ia steroidd egradation:M anna, S.; Yadagiri. P.; Falck. J.R. J. Chem. Sot., Chem. Comm. 1987, 13. 1324-1325. 4. The exploitation of texpenoidsa nd steroids as chirons has been reviewed: Ho, T.-L. Enuntioselective Synfhesk Natural Productsfrom Chiral Terpenes;Jo hn Wiley and Sons, Inc.: New York, 1992. Satisfactorys pectmld ata( 1H (CDC13,250 MHz) and 13c NMR (CDCl3,62.5 MHz), MS) were obtained for all new compounds using chromatographicallyh omogeneouss amples.A ll specific rotations were performed in CHC13. 6. Physical and spectral data for 3: IH NMR: 6 5.09 (br s. lH), 2.35-2.60 (m. 2H), 1.85-2.05( m, 2H), 1.45-1.70 (m, SH), 1.60 (s. 3H). 1.08(s, 3H) 1.04 (s, 3H), 0.95 (s, 3H); 13C NMR: 6 217.6, 132.9, 131.1, 50.0, 47.0, 37.5. 34.68, 34.66, 31.3, 26.6, 23.2, 21.0, 20.8, 20.1; MS (CI, CHI) m/z (rel intensity) 207 (M++l, 80). 189 (100); [a] $? +1&i (c 0.67); 4: {\textquoteleft}H NMR: S 4.92 (app q, J=2.8 Hz, lH), 3.13 (dd, J=5.1, 10.8 Hz, IH), 1.81-l-92 (m, 2H). 1.15-1.61 (m, 7H), 1.49 (br s, 3H), 0.90 (s, 3H), 0.81 (s, 3H). 0.69 (s, 3H); {\textquoteleft}x NMR: 6 134.9, 131.8, 79.3, 50.1, 38.5, 38.5, 37.8, 34.9, 31.9, 27.9, 23.1,21.6, 19.3, 15.2; MS (CI, CH,) m/z (%) 208 (M+, 12). 191 (loo), 175 (24); [a]$? +32 (c 0.65); p-nitrobenzoate of 4 mp: 116-118{\textquoteright}C (EtOH); 5: 1H NMR: 6 5.08 (q, lH, J=1.4 Hz), 3.45 (t, lH, Js2.8 Hz), 1.83-2.10 (m, 2H). 1.58 (d, 3H, J=l.3 Hz),{\textquoteright} 1.20-1.75 (m, 7H). 0.96 (s. 3H), 0.92 (s, 3H), 0.85",
year = "1994",
month = mar,
day = "28",
doi = "10.1016/S0040-4039(00)73036-X",
language = "English (US)",
volume = "35",
pages = "2013--2016",
journal = "Tetrahedron Letters",
issn = "0040-4039",
publisher = "Elsevier Limited",
number = "13",
}