Synthesis and structural anomaly ofxyloketals‐uniquebenzoxacycles: A review

Abstract

Xyloketals, unique bioactive compounds, isolated from mangrove fungus Xylaria sp. (no. 2508), having multiple pharmacological, therapeutic properties, have prompted enormous research on their stereochemistry, bioactivity and synthetic attempts made toward this novel family. This review brings forward a systematic and comprehensive survey of the method of both racemic and enantioselective synthesis, reactivity, and biological properties associated with the xyloketal derivatives and their analogues.

Secondary metabolites from mangrove-associated fungi: source, chemistry and bioactivities

“…77 the mangrove sediment of ZhuHai, Guangdong, China afforded two similar isocoumarin derivatives, (3R*,4S*)-3,4dihydro-4,5,8-trihydroxy-3-methylisocoumarin (126) 81 and (3R*,4S*)-3,4-dihydro-8-hydroxy-4-methoxy-3methylisocoumarin (127). 82 The chemical exploration of three disparate mangrove endophytic fungal strains Eurotium, 83 Cytospora, 84 and Daldinia85 were carried out and afforded four similar new isocoumarins (128)(129)(130)(131), including two isocoumarin ribonic glycosides daldinisides B (130) and C (131). 85 Six new derivatives of 3,4-dihydroisocoumarin 132-137 with an alkyl side chain at C-3 were extracted from four mangrove endophytic fungal strains, such as Aigialus, 86 Setophoma, 87 Epicoccum, 49 and Xylaria.…”

“…Xyloketals are a group of the tetrahydrofurano benzopyran which enclose a highly labile internal ketal in their structure inlay. Their structural diversity and polycyclic skeletons are recognized as one of the pursuits in synthesis to ensure the intact survival of the labile internal ketal system, 131 and endow this family with a wide range of biological activities, such as L-calcium channel blocking activities, 128 neuroprotective actions, 132,133 attenuating fatty acid-induced lipid accumulation, 134 and so on. [135][136][137][138] 3.1.4.…”

Chemoenzymatic Total Synthesis of Natural Products

“…Each member contains at least one 5,6-bicyclic ketal attached to an aromatic core (Figure a) . Isolated xyloketals are chiral with absolute stereochemistry conserved across the family . Xyloketals possess a bicyclic ketal cis -fused with a methyl group on the five-membered ring syn to the hydrogen and methyl substituents at the 5,6-ring fusion, presenting a unique synthetic challenge (Figure a) .…”

“…Suppression of AchE activity decreases acetylcholine’s metabolism, thereby increasing the neurotransmitter levels in the brain. In addition to AchE inhibition, select xyloketals have demonstrated L-calcium channel inhibition, radical-scavenging activity, antioxidant activity, and neuroprotective effects. , …”

“…30 Isolated xyloketals are chiral with absolute stereochemistry conserved across the family. 31 Xyloketals possess a bicyclic ketal cis-fused with a methyl group on the five-membered ring syn to the hydrogen and methyl substituents at the 5,6-ring fusion, presenting a unique synthetic challenge (Figure 2a). 31 Although this class of molecules is relatively small, its members possess a wide range of structural diversity and biological activities (see xyloketals A, B, and D, Figure 2a).…”