The oxa‐Pictet–Spengler cyclization is the oxygen variation of the Pictet–Spengler reaction, in which an aromatic alcohol component (generally a β‐arylethyl alcohol) reacts with acarbonyl component (aldehyde, ketone or their masked derivatives), to yield a 1‐substituted (or 1,1′‐disubstituted)pyran fused to the aromatic ring system found in the starting alcohol. The transformation is usually promoted by Brønsted and Lewis acids. Intramolecular versions of the reaction are also known, where both components are mutually masked as an acetal. Discussed here are aspects concerning the most recent developments and new applications of this useful reaction, including the scope and limitations of new promoters, and new mechanistic pictures of this transformation. The use of novel stereochemical control strategies and the application of the reaction to the synthesis of natural products and their analogs, as well as to accessing fully synthetic bioactive compounds and new ring systems are presented, and chiral versions of the oxa‐Pictet–Spengler are also analyzed.

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The widely varying different approaches to the total synthesis of the indoloquinoline alkaloid neocryptolepine are discussed. Aspects relating to the isolation of the natural prod-

Covering: up to April 2016Aspergillus and Penicillium are fungal species known to produce a high diversity of secondary metabolites, many of them endowed with interesting bioactivity. The small but steadily growing family of the naturally occurring 5-hydroxy-4-aryl-quinolin-2(1H)-one alkaloids and closely related compounds, which represent the results of various research projects that spanned over 20 years and involved scientists from different continents, are covered here. Emphasis is placed on the isolation and chemical structures of the different compounds, together with their source microorganisms, environmental conditions, country or region of origin, and relevant biological activities. In addition, stereochemical aspects, as well as the proposed biosynthetic pathways for the different members, and the incipient synthetic efforts towards some of the compounds or their key intermediates, are discussed in detail.

Naturally-occurring angular tricyclic benzofuran/isobenzofuran derivatives of fungal origin and related compounds, in which two heterocyclic rings are fused to a central benzenoid moiety, are covered. Emphasis is placed on the structure of the compounds, together with their relevant biological activities, source microorganisms, country or region of origin and environmental conditions. In addition, proposed biosynthetic pathways, as well as the total syntheses of some of the compounds, including those that lead to structural revision or to correct stereochemical assignments, and related synthetic efforts, are discussed in detail.

Covering: 2006 to 2018The application of the 6π-azaelectrocyclization of azatrienes as a key strategy for the synthesis of natural products, their analogs and related bioactive or biomedically-relevant compounds (from 2006 to date) is comprehensively reviewed. Details about reaction optimization studies, relevant reaction mechanisms and conditions are also discussed.

Aaptamine, isolated from tropical marine sponges of the Demospongiae class, is the most prominent member of a growing family of natural products. Many aaptaminoids have been shown to have interesting biological activity. The efficient access to 5-methylaaptamine, an unnatural analogue of aaptamine, was achieved by using economic and naturally-occurring eugenol as the starting material. The synthesis involved the preparation of a 5-aminoeugenol derivative through successive nitration, O-methylation, and nitro group reduction reactions.

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