Opening of the Macrocyclic Ring in 5,10:8,9-Disecosteroids ( = Steroklastanes)

✍ Scribed by Ljubinka Lorenc; Lidija Bondarenko-Gheorghiu; Vladimir Pavlović; Hermann Fuhrer; Jaroslav Kalvoda; Mihailo Lj. Mihailović

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: German
• Weight: 496 KB
• Volume: 75
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19920750118

✦ Synopsis

Dedicated to Prof. Vladimir Prelog on the occasion of his 85th birthday (29.X.91) Catalytic hydrogenation of the A '-unsaturated (9R, 10R)-and (9S,lOS)-epoxyenol lactones 3a, b and 4a, b, respectively, affords, in addition to the expected saturated epoxylactones 5a, b and 7a, b, also open-chain products, i.e. the diastereoisomeric (9R, 10R)and (9S,10S)-9,10-epoxy-8-oxo-4,5-secosteroklastan-5-oic acids 6a, b and Sa, b. Alkaline hydrolysis of the lactone ring of compounds 5 and 7 and subsequent acetylation of the corresponding hydroxy derivatives give as the major products the open-chain, diastereoisomeric (9R, 10R)-and (9S, 10S)-4acetoxy-9,10-epoxy-methyl esters 9a, b and l l a , b, respectively, and, but only in the androstane series, the tetrahydropyran derivatives 10a and 12a, as the minor components. Introduction. -As previously reported [ 11 [2], thermal decomposition of steroidal 5a,8a -peroxides of type la, b in boiling AcOH resulted in a cycloreversion-type reaction [3], accompanied by AcOH elimination, to produce the corresponding 5,lO : 8,g-diseco compounds 2a, b, containing a 14-membered ring (fused to ring D) instead of the 'normal' steroid A-B-C ring skeleton (Scheme I)').

It was suggested that by way of this bis-fragmentation as the key step, it could be possible to correlate steroids with some other naturally occurring products containing a 14-membered ring (e.g. cembrenoids, some derivatives of which, isolated from marine organisms, possess significant cytotoxic and antineoplastic activity) or, upon scission of Scheme 1 A, AcOH -AcOH AcO la R=OAc 2a R = AcO (€,€) b R=CaH17 b R = Cab7 (ZE) ') Compounds of the structural type A, i.e. 5,10 :8,9-disecosteroids, were named 'steroklastanes' [2].