P. Wieland

Bio: P. Wieland is an academic researcher from Ciba Specialty Chemicals. The author has contributed to research in topics: Pregnene & Yield (chemistry). The author has an hindex of 18, co-authored 62 publications receiving 1091 citations.

Über die Herstellung mehrkerniger Ketone

Abstract: Ahnlich wie sich 2 Mol Acetessigester und Formaldehyd zum monocyclischen Hagemann'schen Ester in wasseriger Losung kondensieren lassen, fuhrt die analoge Umsetzung von Acetessigester, Acetessigsaure bzw. Acetondicarbonsaure und Formaldehyd mit Derivaten cyclischer Mono- und Diketone schon in wasseriger bzw. wasserig-alkoholischer Losung zur Bildung mehrkerniger cyclischer Ketone.

Reaktionen von Steroid‐Hypojoditen II. Über die Herstellung 18‐oxygenierter Pregnanverbindungen. Über Steroide, 187. Mitteilung

Abstract: The reactions of 20-hydroxypregnanes with iodine and lead tetraacetate, mercuric or silver acetate yield the corresponding oxy radicals. With the latter two reagents, 20-hypoiodites are definitely intermediates. The primary reaction products, i.e. 18-iodo-20-hydroxy compounds, can be oxidized and hydrolized to 18-hydroxy-20-oxo-pregnanes. Under suitable conditions, especially with lead tetraacetate and iodine, a second substitution reaction on carbon 18 of the 18-iodo-20-hydroxy-pregnanes takes place, leading to compounds of the (18 20)-hemiacetal type. These can be oxidized to (18 20)-lactones.

Die Synthese von Acetylen‐carbonyl‐Verbindungen durch Fragmentierung von α, β‐Epoxy‐ketonen mit p‐Toluolsulfonylhydrazin. Vorläufige Mitteilung

Abstract: More than twenty examples illustrate the recently developed oxidoketone-alkynone-fragmentation, whereby α,β-epoxy-ketones are cleaved under mild conditions with p-toluenesulfonyl-hydrazine to give acetylenic ketones or aldehydes.

New substitution reactions in steroids

Abstract: The intramolecular substitution of the angular methyl groups in steroids by attack of O-radicals derived from 6β-, 11β, and 20-alcohols is discussed. Irrespective of their genesis, these radicals abstract a hydrogen atom from one of the said methyl groups, suitably oriented inδ-position. The C-radicals thus formed give different products depending on the neighbouring groups. It is shown that 20-hydroxy-18-C-radicals combine with iodine atoms, to give 18-iodides which can befurther substituted through radicals to give potential 18-oxo-compounds in high yield. In the case of 20-cyanohydrines, the intramolecular reaction of the 18-C-radical with the cyano groups gives rise to the new 18-cyano-20-oxo-steroids. With 6β- and 11β-O-radicalssingle substitution in 19-position predominates, since the steric arrangement of the primary product favours the intramolecular ether formation over a second substitution reaction. A general reaction scheme for these transformations is proposed.

Isolierung, Konstitution und Synthese eines neuen Steroides aus Nebennieren. Über Steroide, 155. Mitteilung

Abstract: A new crystalline substance has been isolated from hog adrenals in a yield of about 30 mg per 1000 kg glands. It appears to act under certain biological conditions as a sodium excreting factor. This compound is shown to be 3β,16α-dihydroxy-allopregnan-20-one; several syntheses of it as well as a number of derivatives are described.

Computer-Assisted Synthetic Planning: The End of the Beginning.

Abstract: Exactly half a century has passed since the launch of the first documented research project (1965 Dendral) on computer-assisted organic synthesis. Many more programs were created in the 1970s and 1980s but the enthusiasm of these pioneering days had largely dissipated by the 2000s, and the challenge of teaching the computer how to plan organic syntheses earned itself the reputation of a "mission impossible". This is quite curious given that, in the meantime, computers have "learned" many other skills that had been considered exclusive domains of human intellect and creativity-for example, machines can nowadays play chess better than human world champions and they can compose classical music pleasant to the human ear. Although there have been no similar feats in organic synthesis, this Review argues that to concede defeat would be premature. Indeed, bringing together the combination of modern computational power and algorithms from graph/network theory, chemical rules (with full stereo- and regiochemistry) coded in appropriate formats, and the elements of quantum mechanics, the machine can finally be "taught" how to plan syntheses of non-trivial organic molecules in a matter of seconds to minutes. The Review begins with an overview of some basic theoretical concepts essential for the big-data analysis of chemical syntheses. It progresses to the problem of optimizing pathways involving known reactions. It culminates with discussion of algorithms that allow for a completely de novo and fully automated design of syntheses leading to relatively complex targets, including those that have not been made before. Of course, there are still things to be improved, but computers are finally becoming relevant and helpful to the practice of organic-synthetic planning. Paraphrasing Churchill's famous words after the Allies' first major victory over the Axis forces in Africa, it is not the end, it is not even the beginning of the end, but it is the end of the beginning for the computer-assisted synthesis planning. The machine is here to stay.

Total Synthesis of Baccatin III and Taxol

Abstract: An intramolecular Heck reaction (90 → 91) serves as the key step in the total synthesis of the titled compounds. The synthetic route is based on utilizing the Wieland−Miescher ketone (5) as a matrix to provide the C and D rings of the targets and to provide functionality implements for joining this sector to an A ring precursor (6). Catalytically induced enantiotopic control and early emplacement of the oxetane are other features of the route.