Selective Wittig olefination in aqueous media for the rapid preparation of unsaturated 7,3-lactone-α-d-xylofuranose derivatives

En Route to Furan-Fused Naphthopyrones: Formal Synthesis of the (+)-Lasionectrin and Its C12-Epimer

“…Motivated by their biological relevance and structural complexity, we launched a research project aimed to develop a concise and modular approach to FFNs in our laboratory. Consequently, it was envisioned the construction of the naphthopyrone core through a [4 + 2] cycloaddition 5 between an ο-quinodimethane intermediate (o-QDM) (generated by heating 1,3-dimethoxy-benzocyclobutenol 7 ) and the unsaturated 7,3-δ-lactone-xylofuranose 8 (7,3-LXF), 6 followed by an oxidative aromatization process of the respective Diels–Alder adduct 9 . On one side, the 1,3-dimethoxy-benzocyclobutenol 7 would provide the required oxygenated functionality within the aromatic system; on the other side, the chiral furan cis -fusion would be provided by the lactone 8 .…”

“…The straightforward preparation of benzocyclobutenol 7 ( 8 ) and chiral furan-fused α,β-unsaturated δ-lactone 8 ( 6 ) from bromo 3,5-dimethoxybenzene and diacetone- d -glucose (DAG), respectively, permitted the rapid execution of the synthesis plan in only six steps ( Scheme 3 ). By refluxing a mixture of two equivalents of 7 with one equivalent of 8 in dry toluene at 150 °C for 18 h in a sealed tube, the Diels–Alder adduct 9 was obtained in 35% yield, along with a dehydrated product 11 in 15% ( Scheme 3 , entry 1).…”

Electrochemical Corey–Winter reaction. Reduction of thiocarbonates in aqueous methanol media and application to the synthesis of a naturally occurring α-pyrone

“…Previously, starting from the versatile chiron 7,3-lactone-xylofuranose ( 7,3-LXF ) [ 6 ], the first non-biological synthesis of chiral 6-pentyl-2 H -pyran-2-ones 1 – 3 was reported by our research group [ 7 ]. These molecules proved to be enantiomers of metabolites isolated from Trichoderma spp and Penicillium isolates .…”

Straighforward Synthesis of a Novel Chiron and its Application to the Synthesis of (+)‐1,4‐Dideoxymannojirimycin and Further Polyoxygenated 2‐Pyperidones

“…The current synthetic strategy for (+)‐ 4 is based on the application of the SHOWO protocol (sequential hydrolysis/oxidation/Wittig olefination) to 6 , giving first the lactam 7 , which is then stereoselectively dihydroxylated and transformed into the title compound by further manipulations of the furanose ring (Scheme ). A stereoselective version of the SHOWO protocol has been successfully employed for the synthesis of the versatile chiron 8 (also known as 7,3‐LXF) starting from diacetone‐D‐glucose (DAG) . Since the success of the stereoselective SHOWO protocol is attributed to the presence of the free hydroxyl group in DAG, which is responsible for the high Z ‐selectivity, we anticipated that the amine group in 6 would behave similarly, thus allowing the preparation of the unsaturated lactam 7 (Scheme ).…”