Benzothiazines in organic synthesis. An approach to floresolide B

Abstract

The intramolecular conjugate addition of a sulfoximine carbanion to an α,β-unsaturated ester results in the formation of a benzothiaine bearing a benzylic stereocenter with extremely high fidelity. We have used this methodology to complete a formal total synthesis of the antitumor agent (+)-floresolide B.

Quinone and Hydroquinone Metabolites from the Ascidians of the Genus Aplidium

“…The synthesis of floresolide B ( 40 ) hydroquinone lactone core was performed by employing ring-closing metathesis approach by Briggs and Dudley [50]. The total synthesis of racemic floresolide B was reported by Nicolaou and Xu, who used an olefin metathesis-based strategy for the formation of the macrocyclic lactone portion [51,52]. …”

Cytotoxic and antioxidant marine prenylated quinones and hydroquinones

“…91 The marine sponge Spongia sp. yielded the cytotoxic metachromins J and K (139 and 140), 100 L and M (141 and 142), 101 S and T (143 and 144), 102 and isometachromin (145). 104 Metachromins J and K exhibited in vitro cytotoxicity (IC 50…”

“…143 The interesting unusual structural architecture of the cytotoxic floresolide B, 172, has prompted its total synthesis by Nicolaou and co-workers 144 and more recently by Chen and Harmata. 145 4.3 Cnidarians 4.3.1 Gorgonians. The cytotoxic prenylated toluhydroquinone moritoside (174), was isolated from the gorgonian Euplexaura sp.…”

Gold(I)-Catalyzed Synthesis of Optically Active 1,4-Oxazepan-7-ones

“…The conversion is efficient, and oxazepanones are prepared in moderate to good yields. Oxazepanones 2 contain two exo methylenes that are poised for further synthetic modifications and are also regarded to be efficient precursors in the synthesis of optically active calvine and the nitrogen analogue of the floresolide B structural motif …”