Chiral decalins: preparation from oleanolic acid and application in the synthesis of (-)-9-epi-ambrox.
A novel and versatile process was developed to prepare the trans-decalins Delta9(11)-3beta-acetoxysclareolide (2) and Delta9(11)-3beta-acetoxy-8-epi-sclareolide (3), respectively, with 4a-methoxycarbonyl-2,7,7-trimethyl-1-oxo-cis-decalin-2-ene (4) and its C-3 hydroxyl derivative 5 from oleanolic acid (3beta-hydroxyolean-12-en-28-oic acid, 1). Three key steps were (a) introduction of the AcO-12 group and the C-9,C-11 double bond at ring C of methyl 3beta-acetoxyolean-12-en-28-oate (8) to afford the diene, methyl 3,12-diacetoxyolean-9(11),12-dien-28-oate (11); (b) photolytic cleavage of the C-8,C-14 bond in the diene to give an acetoxy-substituted triene 14; and (c) oxidative cleavage of the triene or its hydrolyzed alpha,beta-unsaturated ketone product with m-CPBA/TsOH to give the cis- and trans-decalins 2-5. Delata9(11)-3beta-Acetoxysclareolide (2) was stereospecifically reduced to give 3beta-acetoxy-9-epi-sclareolide (23), from which (-)-9-epi-ambrox (7) was synthesized.
Yang
Hai-Jun
HJ
Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, People's Republic of China.
Li
Bo-Gang
BG
Cai
Xiao-Hua
XH
Qi
Hua-Yi
HY
Luo
Ying-Gang
YG
Zhang
Guo-Lin
GL
D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009281:Naphthalenes / Q000138:chemical synthesis* / Q000737:chemistry*; D009828:Oleanolic Acid / Q000737:chemistry*; D010946:Plants, Medicinal / Q000737:chemistry; D013237:Stereoisomerism
D005663:Furans; D009281:Naphthalenes; C413580:ambrox; D009828:Oleanolic Acid; C007229:decalin