scispace - formally typeset
Search or ask a question

Showing papers on "Total synthesis published in 1979"




Journal ArticleDOI
TL;DR: In this paper, a new total synthesis of natural α-tocopherol includes the synthesis of a corresponding (3 R, 7 R)-configurated C15 side chain to be built up by using twice an optically active C5 unit together with an achiral C5 end part.
Abstract: Total Synthesis of Natural α-Tocopherol. I. Preparation of Bifunctional Optically Active Precursors for the Synthesis of the Side Chain by Means of Microbiological Transformations Our concept for a new total synthesis of natural α-tocopherol includes the synthesis of a corresponding (3 R, 7 R)-configurated C15 side chain to be built up by using twice an optically active C5 unit together with an achiral C5 end part. (S)-3-methyl-γ-butyrolactone (11) and (S)-2-methyl-γ-butyrolactone (9) represent suitable bifunctional C5-precursors for this purpose. These two key compounds have been prepared by fermentative transformation including the enantioselective hydrogenation of the double bond of ethyl-4, 4-dimethoxy-3-methylcrotonate (5) by bakers yeast (yielding 11 after ester hydrolysis and cyclization of the fermentation product) and (E)-3-(1′, 3′-dioxolan-2′-yl)-2-buten-1-ol (8) by the fungus Geotrichum candidum (yielding directly 9).

96 citations









Journal ArticleDOI
TL;DR: Pyrrolecarboxylate ester the active insecticidal component in the roots and stems of Ryana speciosa binds nearly irreversibly to sarcoplasmic reticulum vesicles; binding studies intentified calcium release channels now known as Ryanodine receptors.
Abstract: -Pyrrolecarboxylate ester the active insecticidal component in the roots and stems of Ryana speciosa; binds nearly irreversibly to sarcoplasmic reticulum vesicles; binding studies intentified calcium release channels now known as Ryanodine receptors -Originally reported in 1948 by collaborators from Merck and the Department of Entomology at Rutgers University -In 1967, Wiesner and co-workers elucidated the full structure 2 of natural ryanodine -The X-ray structure of the p-bromobenzyl ether 3 of ryanodol was reported in 1972










Journal ArticleDOI
TL;DR: In this article, the total synthesis of 4-formyl-3-hydroxy-8-methoxy-1,9-dimethyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepin-6-carboxylic acid (psoromic acid), a lichen depsidone, by selective functionalization of synthetic methyl 3,8-dimethozy, 1,4, 9-trimethyl- 11-oxO-11h-Dibbnzo[
Abstract: The total synthesis of 4-formyl-3-hydroxy-8-methoxy-1,9-dimethyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepin-6-carboxylic acid (psoromic acid)(28), a lichen depsidone, by selective functionalization of synthetic methyl 3,8-dimethozy-1,4,9-trimethyl-11-oxo-11H-dibbnzo[b,e][1,4]dioxepin-6-carboxylate (methyl O-methylhypopsoromate)(23) and subsequent steps, is described. Attention is drawn to the use of isopropyl ethers as phenol protective groups.







Book ChapterDOI
T. Ross Kelly1
TL;DR: In this article, the synthesis of the anthracyclines is divided into three parts: construction of the aglycones synthesis of sugar residue and coupling of the two.
Abstract: Publisher Summary This chapter analyzes the synthesis of the anthracyclines and their importance as chemotherapeutic agents for the treatment of a broad spectrum of human cancers. The synthesis of the anthracyclines is divided into three parts: construction of the aglycones synthesis of the sugar residue and coupling of the two. The principal synthetic challenges posed by the aglycones include generation of the tetracyclic skeleton, introduction of the A-ring functionality, and achievement of the “correct” regiochemical juxtaposition of the substituents in the A– and D–rings. The demonstration that the natural, cis orientation of the 7- and 9-hydroxyl groups is thermodynamically preferred (∼6:1 ratio) and that epimerization of the C-7 position is affected by CF 3 COOH has attenuated the need to address aglycone stereochemistry directly. Nonetheless, efforts to achieve regiochemically controlled routes have led, inter alia, to a number of new methods of anthraquinone synthesis. In large measure, syntheses of aglycones have relied on the employment of one (or more) of the three general reaction classes: Friedel Crafts alkylations or acylations, nucleophilic condensations, and Diels Alder reactions. The search for effective solutions to aglycone regiochemistry has led to the development of a number of new methods for the construction of anthraquinones that involve anionic species in the regiochemically determining step. Efforts toward the synthesis of the anthracyclines have provided a chemical harvest that is already bounteous and continues to be reaped. Whether total (or partial) synthesis will emerge as the practical solution for the future is, however, a question whose ultimate answer depends on many, as yet, incompletely resolved factors that include: the relative economics of fermentative and total synthesis, the potential therapeutic superiority of non-natural anthracyclines, and the future advances in total synthesis.

Journal ArticleDOI
TL;DR: A total synthesis of ring A aromatic D-homosteroids and the conversion of one of them to estrone and its derivatives is described in this article, where the key reaction is a catalysed addition of 6-methoxy-1-vinyl-3,4...
Abstract: A total synthesis of ring A aromatic D-homosteroids and the conversion of one of them to estrone and its derivatives are described. The key reaction is a catalysed addition of 6-methoxy-1-vinyl-3,4...

Journal ArticleDOI
TL;DR: The Wittig reaction of (R)-(−)-α-cyclocitral with (3-isopropyl-4-methoxybenzyl)-, (4-isooperopyl)-3methoxypodocarpa-8, 11, 13-triene as mentioned in this paper gave (+)-podocarpas-8(14)-en-13-one, a versatile intermediate for natural diterpene synthesis.
Abstract: The Wittig reaction of (R)-(−)-α-cyclocitral with (3-isopropyl-4-methoxybenzyl)-, (4-isopropyl-3-methoxybenzyl)-, and (3-methoxybenzyl) triphenylphosphonium chloride afforded the styryl derivatives which were partially hydrogenated to the corresponding dihydro derivatives (18, 26, and 27). Intramolecular cyclization of 18 and 26 with anhydrous aluminium chloride followed by demethylation with boron tribromide gave (+)-ferruginol and (+)-sempervirol. The similar cyclization of 27 gave (+)-13-methoxypodocarpa-8, 11, 13-triene. This was reduced with lithium in liquid ammonia in the presence of ethanol and then treated with dilute hydrochloric acid to give (+)-podocarpa-8(14)-en-13-one, a versatile intermediate for natural diterpene synthesis.