13 -abeo-Steroids

Neef, G. Eckle, E. Muller-Fahrnow, A. A radical approach to the synthesis of 9(10—>19)abeo-steroids. Tetrahedron 1993, 49, 833-840. 

P-cyano-l8-nor-5ct-tindrostane derivatives. The photolysis of 5-oxo-5-epoxides led to 3 5-dioxo-10(5- 4)abeo steroids. ... 

Diketo-10(5 4)-abeo-steroids from 3-keto-4,5-oxidosteroids... 

Velluz and co-workers named these compounds 19-nor-flfce )-steroids recognizing two possible types, i.e., 0 5A)abeo (127) and 5 0- )abeo (128). " ... 

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). 

Photochemical processes provide an alternative approach to 10(5 - 4)abeo-3,5-diketones. Thus, irradiation of saturated or l,2-unsaturated-4,5-epoxy-3-keto steroids such as (129) and (130) produces 3,5-dioxo-10(5 - 4)abeo-... 

Semisystematic names. Examples of semisystematic parents are corynoxan and labdane. DNP makes widespread use of semisystematic names for terpenoids and steroids (where skeletons such as labdane have not been used in CAS nomenclature since 8C1). lUPAC gives tables of recognised semisystematic parent skeletons and directions for introducing new ones, but in view of the discovery of ever more structurally complex types of natural products, most authors have avoided this route. Semisystematic parents can be modified by operators such as nor-, abeo. 

Terms used to describe modified steroid skeletons include nor (shortening of a side chain or contraction of a ring), homo (expansion of a ring), cyclo (formation of an additional ring), seco (fission of a ring), and abeo (migration of a bond). 

The photorearrangement of the steroidal 1,5-diene-3,7-dione (52) afforded 3,7-dioxo-4,4-dimethyl" 17 /i-acetoxy- i( 10 5a)abeo-6/k 10j8-cycloandrost-l -ene... 

A-Homocholestane derivatives have been obtained by the Demjanov ring-enlargement reaction. Transannular solvolysis reactions have been observed in seco-steroids of type (393) containing a ten-membered ring. Thus, treatment of (393) in aqueous acetone solution produced 5(10—> l H)abeo-5fi-cholest-10(19)-ene 3/8-acetate (394) in high yield. ... 

The 9(10-> l9)-abeo analogue (6) of oestrone methyl ether has been shown by X-ray crystallography to have the normal 9a -configuration, but because of the chair conformation of the enlarged ring b the molecule differs considerably in shape from oestrone methyl ether. X-Ray, n.m.r., and o.r.d. data establish the structures and absolute configurations of a series of insect-repellent steroids isolated from Nicandra physaloides. The structure and conformation of the 6-sila-steroid (7) have been determined. ... 

Important, naturally occurring derivatives are quoted in brackets. Sapogenins and steroid alcohols contain hetero atoms linked with the side chain and ring D the cardenolides and bufadienolides possess an imsaturated 5 or 6-ring lactone instead of the chain at C l as well as cis C/D fusion. In synthetic steroid chemistry, one frequently encounters derivatives which have been formed by shortening, lengtheniug, opening, transformation or introduction of hetero atoms they are named after the fundamental skeleton with terms like nor-, homo-, seco-, abeo-, azasteroids etc. Reference must be made to the specialist literature on steroid chemistry for detailed information (e. g., [55, 108]). 

C-nor-D-homo- or [14(13 2)-abeo] systems. The latter, also referred to as Solanum alkaloids, share a common ABCD steroid skeleton, i.e., six-membered C-rings and five-membered D-rings. The Veratrum alkaloids are further divided into three subgroups (see Figure 1) the jervanine, the veratramine, and the cevanine. The Solanum alkaloids on the other hand, are further divided into the solanidine and verazine subgroups (see Figure 1). 

Thus, the C27-steroid alkaloids with C-nor-D-homo [14(13->-12)-abeo] ring system, that is, with a jervane (5) or cevane (6) skeleton, found in Liliaceae but until now not in Solanaceae, are not included they will be described exhaustively in another chapter of this volume by S. M. Kupchan. On the other hand, the tertiary Veratrum bases rubijervine, isorubijervine, and veralobine belong to the solanidanes and will be mentioned briefly in this chapter, but a detailed description of these alkaloids and their derivatives will also be given by S. M. Kupchan. 

Aoki, S., Watanabe, Y, Tanabe, D., Setiawan, A., Arai, M., and Kobayashi, M. (2007a) Cortistatins J, K, L, novel abeo-9(10-19)-androstane-type steroidal alkaloids with isoquinoline unit, from marine sponge Corticium simplex. Tetrahedron Lett., 48, 4485— 4488. 

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