Synthesen in der Reihe der Steroide

Abstract

Is Steroide bezeichnet man eine Gruppe von Natur-A stoffen, die sich vom gleichen Ringgerlist Wie die Sterhe ahleiten, die also Derivate des hydrierten Cyclopentenophenanthrens (I) sind. Die Abkommlinge dieses einfachen Ringgertists haben in den letzten Jahren ein sehr allgemeines Interesse erlangt; nian darf wohl sagen, da5 die Vielseitigkeit der biologkhen Wirkung der Steroide einzig dastehend ist. In diese grofk Klasse von Naturstoffen gehoren die Sterine, die Gallensffuren, das antirachitische Vitamin, die miinnlichen und weiblichen Sexualhormone, das Nebennierenrindenhormon und die pflamlichen und tierischen Herzgifte. Vor einigen Jahren ist zusammenfassend in dieser Zeitschrift i i k die amlytische Untersuchung der Sterine und Gallen-&wen1) und der Sexualhormone*) berichtet worden. Fh sei daher nur noch einmal an die Konstitutionsformeln von hier interessierenden Vertretem einzelner Stoffklassen erinnert.Das Formelbild (11) gibt die Struktur des wichtigsten tierischen Sterins, des Cholesterins wieder, dessen Konstitrrtionserniittlrmg von Widzu.9 in langj-er Arbeit durchgefiihrt und 1932 zum Abschltd ge-

Organocatalytic Asymmetric Formation of Steroids

“…EWG = electronwithdrawing group. [8][9][10][11][12][13] Our novel approach is based on the condensation of an aminocatalyst with an enal or 2,4-dienal to form either a dienamine or trienamine, respectively, which consist of a diene moiety attached to an activating and stereoinducing molecular handle. [20] A more recent development is the application of organocatalysis in targetoriented synthesis.…”

“…[7] In the 1930s, Dane attempted this strategy, which was based on a cycloaddition between what became known as Danes diene and a dienophile. [8] Later Quinkert et al showed that the Diels-Alder reaction could be promoted by the application of a Lewis acid catalyst. [9] Recently, enantioselective versions of this approach, based on the activation of different dienophiles with chiral catalysts, have been reported (Scheme 1 a).…”

“…Previous reports, which focus on the activation of the dienophilic partner of the reaction, are all shown to react with Danes diene, which is electron rich because of the conjugated methoxy substituent in the A ring. [8][9][10][11][12][13] Our novel approach is based on the condensation of an aminocatalyst with an enal or 2,4-dienal to form either a dienamine or trienamine, respectively, which consist of a diene moiety attached to an activating and stereoinducing molecular handle. Because of the electron donation from the catalyst the reaction can be performed with a wide range of easily available substrates.…”

“…Synthesis of Torgov's diene(8), thus leading to a formal synthesis of (+)-estrone from 4 a. See the Supporting Information for details.…”

Ab + D → Abcd

“…The diene 1 has been condensed with numerous other dienophiles [15][16][17][18][19][20][21][22][23][24][25]29], as has 16 [26][27][28]30]. A wide variety of dienes has been utilized, many of them by a Russian group associated with I. N. Nazarov.…”