01533nas a2200169 4500008004100000022001400041245015500055210006900210260000800279300001400287490000700301520085700308100002301165700002401188700002201212856012901234 2019 eng d a1477-052000aTiCl4-n-Bu3N-mediated cascade annulation of ketones with alpha-ketoesters: a facile synthesis of highly substituted fused gamma-alkylidene-butenolides0 aTiCl4nBu3Nmediated cascade annulation of ketones with alphaketoe cJUN a5749-57590 v173 a

A facile protocol for the synthesis of highly substituted fused gamma-alkylidene butenolides using direct annulation of ketones with alpha-ketoesters, which proceeds through TiCl4-n-Bu3N mediated aldol addition followed by an intramolecular enol-lactonization/cyclization cascade, is reported. Diverse 6-5, 7-5 and 8-5 fused bicyclic gamma-ylidene butenolides and highly substituted monocyclic analogs related to biologically relevant natural products were prepared from readily accessible ketone and alpha-ketoester building blocks. The highly step-economic cascade nature, good substrate scope, easy access to complex products with good to excellent yields, gram-scalability, demonstration of synthetic utility, and unambiguous structural confirmation through X-ray crystallography analyses and analogy are the salient features of this work.

1 aPalange, Megha, N.1 aGonnade, Rajesh, G.1 aKontham, Ravindar uhttps://library.ncl.res.in/content/ticl4-n-bu3n-mediated-cascade-annulation-ketones-alpha-ketoesters-facile-synthesis-highly01390nas a2200169 4500008004100000022001400041245007500055210006900130260000900199300001400208490000700222520082100229100002601050700001701076700002201093856010501115 2020 eng d a1523-706000aTotal synthesis of beshanzuenone D and its epimers and abiespiroside A0 aTotal synthesis of beshanzuenone D and its epimers and abiespiro cNOV  a8561-85650 v223 a

A unified and protecting-group-free six-step total synthesis of bisabolane-type sesquiterpenoid beshanzuenone D and its stereoisomers and abiespiroside A using S-(+)-carvone as a common chiral-pool building block is disclosed. This synthetic route features chemoselective allylic chlorination of carvone, Au(I)-catalyzed cydoisomerization induced construction of furan from homopropargylic diol, substrate-controlled selective hydroxylation using Davis-oxaziridine, and dye-sensitized photo-oxidation (through O-1(2)) of hydroxyalkyl tethered furan to access oxaspirolactone as key transformations. A comprehensive set of NMR data along with DFT calculations, ECD spectra, and optical rotation measurements of the synthesized beshanzuenone D and its epimers were obtained to confirm absolute configurations.

1 aBorade, Balasaheb, R.1 aDixit, Ruchi1 aKontham, Ravindar uhttps://library.ncl.res.in/content/total-synthesis-beshanzuenone-d-and-its-epimers-and-abiespiroside01374nas a2200169 4500008004100000022001400041245008100055210006900136260000800205300001400213490000700227520079000234100002401024700002301048700002201071856011101093 2025 eng d a1477-052000aTotal synthesis of linear lipodepsipeptide kavaratamide A and its C25-epimer0 aTotal synthesis of linear lipodepsipeptide kavaratamide A and it cFEB a1819-18220 v233 a

We report the stereoselective total synthesis of kavaratamide A, a linear lipodepsipeptide from the cyanobacterium Moorena bouillonii (collected in Kavaratti, India), and its unnatural C25-epimer. The convergent approach employs Keck asymmetric allylation to construct the chiral beta-hydroxy carboxylic acid fragment [(3S)-HDA; 3-hydroxydecanoic acid], while the peptide unit was assembled from l-Val, N-Me-l-Ala, (S)-Hiva, and (S)-iPr-O-Me-pyr using well-orchestrated coupling methods to prevent racemization. Modifications to the Keck allylation conditions enabled the synthesis of the C25-epimer with good yield. Cytotoxicity of kavaratamide A and C25-epi-kavaratamide A, assessed using the MTT assay, demonstrated moderate activity against HepG2 and PANC-1 cell lines.

1 aSahu, Manas, Ranjan1 aIngale, Sudhir, R.1 aKontham, Ravindar uhttps://library.ncl.res.in/content/total-synthesis-linear-lipodepsipeptide-kavaratamide-and-its-c25-epimer