Alkaloids, steroidal rearrangements

The C-nor-D-homosteroid rearrangement was discovered by Hirschmann and co-workers at the time that Wintersteiner and his collaborators established that the steroid alkaloids jervine and veratramine incorporate a 14 (1312) abeo-nng system. This was the predecessor of the family of simultaneous ring contraction-expansion reactions. Solvolysis of the 12j5-methanesulfonate (144a) gives mainly the kinetic reaction product, the C-nor-D-homo exocyclic olefin (145) along with some 13(17)-ene (146a). 

Steroidal amines with nitrogen at C-3 or C-20 can be converted into steroidal hormones." Beckmann rearrangement of the oxime (45) of funtumine gives 3a,17j3-diamino-5a-androstane (46). Ruschig deamination of the latter gives androstanedione In the same way, the alkaloids of H. floribunda,... 

Veralkamine and veralinine are regarded as derivatives of the rearranged steroid hydrocarbon cholestane (5). However, there are also alkaloids possessing a normal cholestane skeleton (the 22,26-epiminocholestanes cf. Vol. X, p. 60). 

Veramine (124) is the first known member of a steroidal alkaloid type with the rearranged tomatanine skeleton 75, 76). Seleninm dehydrogenation of 124 afforded, in addition to 2-ethyl-5-methylpyridine... 

Easic Principles Practical Photochemistry General Considerations Carbonyl Compounds a-Cleavage Carbonyl Compounds Hydrogren Abstraction Steroids Carbonyl Compounds Cycloaddition Enone and Dienone Rearrangements Alkenes Isomerisation and Rearrangement Alkenes Cycloaddition Alkenes Photo-Cxidation Terpenoids Aromatic Compounds Isomerisation and Cycloaddition Practical Photochemistry Scale-up Aromatic Compounds Substitution and Cydisation Alkaloids Photoinitiated Free-radical Chain Reactions. 

Biosynthesis These alkaloids are formed by the usual plant steroid biosynthetic pathway via cycloartenol and cholesterol. The Solanum steroid alkaloids and procevine (22/J,255)-18,22,26-nitrilocholest-5-en-3/S-ol, CAS [468-24-6] also present in Liliaceae are important intermediates in these processes and furnish all the other types of compounds by carbon skeleton rearrangement and ring closure reactions. ... 

Oxanorbomenes are valuable substrates for RRM processes as weU [8], Thus, a smooth rearrangement of the 7-oxabicyclo[2.2.1]heptene 30 via domino ROM/ double RCM occurred on treatment with the second-generation Grubbs catalyst 2 under ethylene-free conditions (Scheme 2.12) [8b], The spiro compound 31 produced with high efficacy represents the DEF ring fragment of steroidal alkaloid cyclopamine. 

The C-nor-D-homo steroid alkaloids are formed from steroids by rearrangement of the ring system. The exact pathway is, however, still unknown. The alkaloids are poisonous to animals and act as feeding deterrents (E 5.5.3). They are effective insecticides. 

Alkoxycyclopropane ring rearrangements have been -used in the synthesis of several terpenes. Steroids can be obtained by a cobalt-catalyzed stereospecific triple ring closure of enediynes . Practical routes for large-scale preparation of Cinchona alkaloids and their analogs, including the preparation of quinine and quinidine by a highly stereospecific autoxidation, have been founds . 

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