The angular trifluoromethyl group. V. Total synthesis and biological properties of 14-dehydro-18,18,18-trifluoro-19-nortestosterone

Asymmetric Total Synthesis of the Indole Diterpene Alkaloid Paspaline

“…The steric impact of the C12c methyl group on the outcome of this reaction cannot be overstated; ketone reduction in analogous steroidal systems not bearing this methyl group generally proceed with the opposite sense of selectivity. 39,41 …”

Synthesis of Diastereomeric 8‐Fluoro‐ABC‐Steroid Building Blocks

“…The subsequent reductive decyanation of 7-(fluorohex-5enyl)-3-methoxybicyclo[4.2.0]octa-1,3,5-triene-7-carbonitrile (38) and its contaminants was executed analogously to Kametani's prescription [57] with sodium in ammonia in the presence of isopropanol as the proton source (Scheme 5). The crude the only reaction leading to 42 c (R=H) since this alkene was present at 33 % in the product mixture.…”

“…In 1994, Wakselman et al described the synthesis of a 14-dehydro-18,18,18-trifluoro-19nortestosterone, in which the steroid 14 was obtained from 12 in 48 % yield as a mixture of diastereomers (5 : 1) via the intermediate o-quinodimethane 13 (Scheme 2). [38] However, in this reaction the trifluoromethyl group was attached remote of the reaction center.…”

“…[21] Using either of these methods, steroids with fluorine in almost all positions could be synthesized, as exemplified by the following references, which were published after those reviewed in references. [12][13][14][15][16][17] Steroids with fluorine substituents in 1-, [22,23] 2-, [22,23] 3-, [24] 4-, [22] 5-, [21,22,25] 6-, [21,26,27] 7-, [28] 9-, [1] 10-, [24,29] 11-, [24] 12-, [30] 14-, [30] 15-, [30] 16-, [31][32][33][34] 17-, [24,35] 18-, [36][37][38] and 19position [39][40][41][42] were obtained.…”

A Global and Local Desymmetrization Approach to the Synthesis of Steroidal Alkaloids: Stereocontrolled Total Synthesis of Paspaline

“…23 Indeed, reduction of 22 upon treatment with LiAlH 4 gave exclusively the ( S )-hydroxyl 23 in 60% yield over two steps. The stereochemistry of this reaction is of note in that reduction of analogous compounds not bearing the C12a angular methyl group in 1 have proceeded with selectivity orthogonal to that observed in 23 , 22,24 giving evidence to the impact of this methyl group in facial preference of the ketone in 22 . Catalytic hydrogenation of 23 using Crabtree’s catalyst and subsequent oxidation gave ketone 24 in 86% yield over two steps with complete concave surface selectivity.…”