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Stereoselective Synthesis of 5a‐Ethyl‐1,2,3,3a,4,5,5a,6,9a,9b‐decahydro‐ 1,3,4‐trihydroxy‐3a‐(hydroxymethyl)‐7 H ‐benz[ e ]inden‐7‐one Derivatives
Author(s) -
Mosimann Hervé,
Vogel Pierre
Publication year - 1999
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19990908)82:9<1371::aid-hlca1371>3.0.co;2-n
Subject(s) - chemistry , furan , stereochemistry , alcohol , stereoselectivity , hydroxymethyl , pinacol , medicinal chemistry , catalysis , organic chemistry
Homochiral Diels‐Alder cyclodimerization of (±)‐6‐ethenyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐ endo ‐ol ( 1 ) followed by oxidation gives (1 RS ,4 RS ,4a SR ,4b SR ,5 RS ,8 RS ,8a RS )‐8a‐ethenyl‐1,3,4,4a,4b,5,6,8,8a,9‐decahydro‐1,4:5,8‐diepoxyphenanthrene‐2,7‐dione ( 18 ). Selective hydrogenation followed by epoxidation produced (1 RS ,4 RS ,4a RS ,5a RS ,6a RS ,7 RS ,10 RS ,10a SR ,10b RS )‐6a‐ethyl‐1,4,5a,6,6a,7,9,10,10a,10b‐decahydro‐1,4:7,10‐diepoxyphenanthro[8a,9‐ b ]oxirene‐3,8‐dione ( 21 ), which was solvolyzed (Me 3 SiOSO 2 CF 3 , Piv 2 O) with concomitant pinacol rearrangement involving an acyl‐group migration to give a 6‐oxo‐7‐oxabicyclo[2.2.1]hept‐2‐yl cation intermediate, which finally generated (1 RS ,3 SR ,3a RS ,4 SR ,5a RS ,6 RS ,9 RS ,9a SR ,9b SR )‐5a‐ethyl‐1,4,5,5a,6,7,8,9,9a,9b‐decahydro‐7,10‐dioxo‐3 H ‐6,9‐epoxy‐1,3a‐ethanonaphtho[1,2‐ c ]furan‐3,4‐diyl bis(2,2‐dimethylpropanoate) ( 24 ). Photo‐reductive 7‐oxa bridge opening of 24 , followed by water elimination and silylation, provided (1 RS ,3 SR ,3a RS ,4 SR ,5a SR ,9a SR ,9b SR )‐7‐{[( tert ‐butyl)dimethylsilyl]oxy}‐5a‐ethyl‐1,4,5,5a,9a,9b‐hexahydro‐10‐oxo‐3 H ‐1,3‐ethanonaphtho[1,2‐ c ]furan‐3,4‐diyl bis(2,2‐dimethylpropanoate) ( 34 ). Reduction of 34 with NaBH 4 in MeOH followed by desilylation and alcohol protection produced (1 RS ,3 RS ,3a RS ,4 SR ,5a SR ,9a SR ,9b SR )‐5a‐ethyl‐2,3,3a,4,5,5a,6,7,9a,9b‐decahydro‐1,3‐bis(methoxymethoxy)‐3a‐[(methoxymethoxy)methyl]‐7‐oxo‐1 H ‐benz[ e ]inden‐4‐yl 2,2‐dimethylpropanoate ( 5 ), a polyoxy‐substituted decahydro‐1 H ‐benz[ e ]indene derivative with cis‐transoid ‐ trans junction for the two cyclohexane and the cyclopentane rings bearing an angular 3a‐(oxymethyl) substituent.