01532nas a2200157   4500008004100000022001400041245008900055210006900144260000800213300001600221490000700237520097100244100002601215700002201241856011101263       2022                        eng d  a0022-326300aConcise total synthesis of (+)-lanceolactone a: revision of absolute stereochemistry0 aConcise total synthesis of lanceolactone a revision of absolute   cOCT  a12867-128760 v873 a<p>
	A chiral-pool protecting-group-free five-step total synthesis of tetranorsesquiterpenoide (+)-lanceolactone A and all of its four stereoisomers using (S)-(+)-, and (R)-(-)-linalool (coriandrol) as building blocks is disclosed. The key steps involved in this synthetic route are regioselective ozonolysis, Au(I)-catalyzed cycloisomerization-induced construction of furan from alleneone, and dye-sensitized photo-oxidation (through O-1(2) ; singlet oxygen) of hydroxyalkyl-tethered furan to access oxaspirolactone. After a thorough evaluation of electronic circular dichroism (ECD) and optical rotation data of all possible stereoisomers, the absolute configuration of natural lanceolactone A at the C4 and C7 positions has been assigned as (+)-(4S,7S), which is an enantiomer to the initially proposed structure (+)-(4R,7R). Further, these investigations led us to extend Feringa and Gawronski's CD correlation method to [5,5]- and [6,5]-oxaspirolactones.</p>
1 aBorade, Balasaheb, R.1 aKontham, Ravindar  uhttps://library.ncl.res.in/content/concise-total-synthesis-lanceolactone-revision-absolute-stereochemistry02021nas a2200169   4500008004100000022001400041245012400055210006900179260000900248300001400257490000700271520137100278100003201649700002201681700002201703856012601725       2024                        eng d  a1477-052000aConcise and collective total syntheses of 2,4-disubstituted furan-derived natural products from hydroxyoxetanyl ketones0 aConcise and collective total syntheses of 24disubstituted furand  cFEB   a1475-14830 v223 a<p>
	The furan moiety, prevalent in bioactive natural products and essential drugs, presents intriguing structural features that have spurred our exploration into streamlined chemical synthesis routes for related natural products. In this study, we demonstrate the concise total synthesis of eight 2,4-disubstituted furan-derived natural products (including methylfuroic acid, rabdoketones A and B, paleofurans A and B, tournefolin C, and shikonofurans A and B). Our methodology revolves around the utilization of hydroxyoxetanyl ketones as pivotal intermediates. The approach encompasses transformations such as selective organo-catalyzed cross-ketol addition, synthesis of hydroxymethyl-tethered furans through Bi(OTf)3 catalyzed dehydrative cycloisomerization of alpha-hydroxyoxetanyl ketones, and a hydrogen atom transfer (HAT)-mediated oxidation of primary alcohols into the corresponding acids. This comprehensive synthetic strategy highlights the versatility of hydroxyoxetanyl ketones as invaluable building blocks in the synthesis of furan-containing natural products. A unified total synthesis of eight 2,4-disubstituted furan-derived natural products has been achieved through Bi(iii)-catalyzed cascade cycloisomerization of alpha-hydroxyoxetanyl ketones and hydrogen atom transfer-mediated oxidation of primary alcohols as pivotal transformations.</p>
1 aSahoo, Shubhranshu, Shekhar1 aKataria, Priyanka1 aKontham, Ravindar  uhttps://library.ncl.res.in/content/concise-and-collective-total-syntheses-24-disubstituted-furan-derived-natural-products