Changing the Reaction Pathway of Silyl-Prins Cyclization by Switching the Lewis Acid: Application to the Synthesis of an Antinociceptive Compound.

Developing new procedures for the synthesis of tetrahydropyrans in a very stereoselective manner is of great importance for the synthesis of THP-containing natural products. Here, we report an interesting protocol for the synthesis of polysubstituted halogenated tetrahydropyrans by silyl-Prins cyclization of vinylsilyl alcohols, in which the nature of the Lewis acid determines the outcome of the process. The methodology has been applied to the synthesis of a known antinociceptive.

Synthesis and applications of the sulfur containing analogues of cyclic carbonates.

Cyclic thiocarbonates are the sulfur containing analogues of the well-studied cyclic carbonates and are relatively poorly explored despite their potential applications and intriguing reactivities. To date, application of these organosulfur compounds has included their use as monomers for polythiocarbonate synthesis (their ring-opening is more readily achieved and more selective than the corresponding cyclic carbonates) and as reactive intermediates for the preparation of a range of higher-value sulfur containing compounds. Despite these uses, the synthesis of these compounds is far less explored and developed than their non-sulfur analogues.

Group 13 salphen compounds (In, Ga and Al): a comparison of their structural features and activities as catalysts for cyclic carbonate synthesis.

Many complexes based on group 13 elements have been successfully applied as catalysts for the synthesis of cyclic carbonates from epoxides and CO and to date these have provided some of the most active catalysts developed. It is notable that most reports have focused on the use of aluminium-based compounds likely because of the well-established Lewis acidity of this element and its cost. In comparison, relatively little attention has been paid to the development of catalysts based on the heavier group 13 elements, despite their known Lewis acidic properties.

The Tetrahydrofuran Motif in Marine Lipids and Terpenes.

Heterocycles are particularly common moieties within marine natural products. Specifically, tetrahydrofuranyl rings are present in a variety of compounds which present complex structures and interesting biological activities. Focusing on terpenoids, a high number of tetrahydrofuran-containing metabolites have been isolated during the last decades.

The Tetrahydrofuran Motif in Polyketide Marine Drugs.

Oxygen heterocycles are units that are abundant in a great number of marine natural products. Among them, marine polyketides containing tetrahydrofuran rings have attracted great attention within the scientific community due to their challenging structures and promising biological activities. An overview of the most important marine tetrahydrofuran polyketides, with a focused discussion on their isolation, structure determination, approaches to their total synthesis, and biological studies is provided.

Influence of the Substituents on the Opening of Silylepoxy Alcohols: 5--Cyclization towards Tetrahydrofurans vs. Unexpected Side Reaction Leading to Tetrahydropyrans.

The regioselective ring opening of epoxy alcohols is an effective method for the synthesis of different types of oxacycles. The 5- opening being preferred vs. the 6- mode, according to Baldwin rules, the use of silyl-substituted oxiranes has been reported as a possible method to favor the 6- cyclization.

Unexpected Domino Silyl-Prins/Aryl Migration Process from Geminal Vinylsilyl Alcohols.

The silyl-Prins cyclization of geminal vinylsilyl alcohols and aldehydes, promoted by TMSOTf, provides access to polysubstituted tetrahydropyrans in which the silyl group remains in the molecule and an aryl group has migrated from silicon to carbon. This domino silyl-Prins/aryl migration process is general and high-yielding for aryl, vinyl, or alkyl aldehydes. Moreover, cyclization proceeds with very high stereocontrol in a one-pot reaction in which both quaternary and tertiary stereogenic centers have been created.

Marine Heterocyclic Compounds That Modulate Intracellular Calcium Signals: Chemistry and Synthesis Approaches.

Intracellular Ca plays a pivotal role in the control of a large series of cell functions in all types of cells, from neurotransmitter release and muscle contraction to gene expression, cell proliferation and cell death. Ca is transported through specific channels and transporters in the plasma membrane and subcellular organelles such as the endoplasmic reticulum and mitochondria. Therefore, dysregulation of intracellular Ca homeostasis may lead to cell dysfunction and disease.

Synthesis of Polysubstituted Tetrahydropyrans by Stereoselective Hydroalkoxylation of Silyl Alkenols: En Route to Tetrahydropyranyl Marine Analogues.

Tetrahydropyrans are abundantly found in marine natural products. The interesting biological properties of these compounds and their analogues make necessary the development of convenient procedures for their synthesis. In this paper, an atom economy access to tetrahydropyrans by intramolecular acid-mediated cyclization of silylated alkenols is described.

The Oxepane Motif in Marine Drugs.

Oceans have shown to be a remarkable source of natural products. The biological properties of many of these compounds have helped to produce great advances in medicinal chemistry. Within them, marine natural products containing an oxepanyl ring are present in a great variety of algae, sponges, fungus and corals and show very important biological activities, many of them possessing remarkable cytotoxic properties against a wide range of cancer cell lines.