Alkaloids, steroidal synthesis, total

Soon after returning to the Shionogi Research Laboratories from the University of Basel, he became Section Manager to pursue the total synthesis of steroids. This work led to total or partial synthesis of the racemic form of many steroids and steroidal alkaloids, such as estrone 3-methyl ether, 3a-acetoxy-5/3-pregna-9(ll), 16-dien-20-one, aldosterone, latifoline, and cones-sine (1961-1963). With extensive support and encouragement from the late... 

Total synthesis of complex (macrocyclic) natural products using fast and flexible strategies and diversity-oriented synthesis of natural product-like macrocycles are important research topics in our laboratory. The following sections describe the total synthesis of epothilone D and epothilone D5 analogues, DOS of cyclopeptide alkaloid analogues, of biaryl ether macrocycles, and of steroid/peptide hybrid macrocycles, respectively. 

These preliminary results have been used to support a formal total synthesis of a precursor of (+ )-conessine, a steroidal alkaloid used in the treatment of dysentery 432... 

Solanidine-type steroid alkaloids, synthesis and reactions 88MI6I. Streptonigrin, total syntheses of 84MI30. 

A unique class of steroidal alkaloids, the batrachotoxinins, is isolated in small quantities from the skins of poison arrow frogs and also from the feather of a New Guinea bird. One of the key steps during the total synthesis of (+)-batrachotoxinin A by Y. Kishi et al. was a Michael addition to form a seven-membered oxazapane ring. The removal of the primary TBS protecting group was achieved by treatment with TASF and the resulting alkoxide attacked the enone at the 3-position to afford an enolate as the Michael adduct. The enolate was trapped with phenyl triflimide as the end triflate. 

Studies on the total synthesis of batrachotoxins (steroid alkaloids found in the skin of frogs of the Phyllobates species and the feathers of birds of the Pitohui and Iflita families from New Guinea) 04YGK1205. 

From the extensive chemical experience of the last decade in the stereochemistry and synthesis of fused ring systems related to steroids, alkaloids, resin acids, and terpenes and in the synthesis and reactions of tropolones, one might be led to the erroneous conclusion that the total synthesis of colchicine should not be difficult. Preliminary studies in this direction have been reported by many workers, but the ultimate goal has yet to be reached. 

Heterocyclic, ar. aldehydes—Total synthesis of steroidal sapogenins and certain steroidal alkaloids s. 16, 320... 

Six-membered 5-thiolactams represent by far the largest number of examples. The steroidal thiolactam (96) is formed chemo-selectively. The )V-methyl-5-lactam moiety of the antibiotic marcfortine A is selectively thionated to 18-thiomarcfortine A (97) while the unsubstituted y-lactam group is not attacked by LR. The optically active 5-thiolactam (98) is a useful intermediate for the total synthesis of the alkaloid prosopinine. ... 

In the total synthesis of o-Homosteroid, Tietze et al. reported a BF3-OEt2-catalyzed cascade [1,5]-hydride transfer/cyclization of 219, which produced an unusually bridged steroid alkaloid 220 in 85 % yield at room temperature (Scheme 84) [137-139]. Although benzylic methine and imine in 219 are comparatively inactive hydride donor and acceptor, with the assistance of electron-donating methoxy group... 

Among noteworthy recent achievements may also be mentioned the total synthesis of steroidal sapogenins and certain steroidal alkaloids , of griseofulvin independently by two groups , of chlorophyll and of coenzyme A, a complex nucleoside diphosphate... 

Introduction - The year saw an es losion in the number of publications on the total synthesis of steroids and especially estratriene derivatives. Research in the field of steroidal alkaloids is also reaching monumental proportions and is fast becoming the single most active field of steroid chemistry. For example recent work by Kyoto chemists has led to the isolation and identification of 2J pregnane alkaloids from the common Pachi sandra Terminali s. ... 

CrOg added slowly with cooling to dry pyridine, then a soln. of 3,16-biscyclo-ethylenedioxybisnor-5a-cholan-22-ol in pyridine added dropwise, and kept 4 hrs. at 37° 3,16-biscycloethylenedioxybisnor-5a-cholan-22-al. Y 83%.—The un usually high yield is due to the sterically hindered 22-position.—This is a stage in a total synthesis of steroidal sapogenlns and certain steroidal alkaloids. Y. Mazur, N. Danieli, and F. Sondheimer, Am. Soc. 82, 5889 (1960) heterocyclic, ar. aldehydes, at reflux temp., s. W. Korytnyk and E. J. Kris, Chem. Ind. 1961, 1834. 

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