Diastereoselective Synthesis of Highly Functionalized Tetrahydroxanthenols—Unprecedented Access to Privileged Structural Motifs

Abstract

Tetrahydroxanthenones, which can be easily prepared by a domino oxa-Michael aldol condensation, offer various possibilities for diastereoselective functionalization, giving access to the stereocontrolled synthesis of stereochemical triades or tetrades, which represent privileged structural motifs. In most cases, the relative stereochemistry was unequivocally established by crystal structure analysis.

2‐Iodoxybenzoic Acid—A Simple Oxidant with a Dazzling Array of Potential Applications

“…[218] A closely related reaction that involves the use of IBX in the presence of InCl 3 leads to a,b-unsaturated lactones. [219] The cyclization of unsaturated N-aryl amides in the presence of IBX represents a reaction type, the synthetic potential of which has certainly not yet been fully explored. Detailed studies by Nicolaou et al demonstrated that CÀN bond formation occurs at elevated temperature through a reactivity of IBX that is fundamentally different from most of the reactions discussed previously.…”

The Diels–Alder Approach to Δ9‐Tetrahydrocannabinol Derivatives

“…[38,39] This cascade reaction leads directly to formyl chromene 13, which can then be converted into diene 7a with a Wittig reaction (Scheme 2), as demonstrated in previous work from our group. Another route to diene 7, which has an unsubstituted benzochromone scaffold, involves a domino oxa-Michael-aldol reaction of the corresponding salicylaldehyde with prenal, as described previously.…”

2‐Iodoxybenzoesäure – ein einfaches Oxidationsmittel mit einer Vielfalt an Anwendungsmöglichkeiten

“…[218] Eine verwandte Reaktion mit IBX in Gegenwart von InCl 3 führt zur Bildung a,b-ungesättigter Lactone. [219] Eine Reaktion, deren Synthesepotenzial noch nicht annähernd offenbart wurde, ist sicherlich die Cyclisierung von ungesättigten N-Arylamiden in Gegenwart von IBX. Nicolaou et al haben in detaillierten Studien gezeigt, dass bei er-Schema 59.…”