Synthesis of the C8–C20 and C21–C30 segments of pectenotoxin 2

Synthesis, Structural Elucidation, and Biological Evaluation of NSC12, an Orally Available Fibroblast Growth Factor (FGF) Ligand Trap for the Treatment of FGF-Dependent Lung Tumors

“…While compound 11 showed a NOE contact between H18 and H21a at 2.18 ppm, compound 9 showed a signal at 2.05 ppm that could not be unequivocally identified by 2D-COSY nor by HSQC-NMR experiments, due to extensive signal overlapping from protons of the steroidal skeleton (Figure ). We thus decided to engage the C20 and C22 hydroxyl groups in a six-membered cyclic carbonate (Scheme ) to shift some of the critical signals in the NMR spectra and “freeze” the conformation accessible to the 1,3-diol portion. , The energy-minimized geometries of carbonates 12 and 13 (Figure ) allowed the calculation of the distance between H21a and H18, found to be 4.33 and 2.46 Å for the 20 R and 20 S carbonates, respectively. 1 H NMR analysis of cyclic carbonates showed that H20 retained the triplet multiplicity and that the critical pseudoequatorial H21a signal was in a region of the spectrum free of other resonance peaks.…”

Total Synthesis of Methyl Sarcophytoate, a Marine Natural Biscembranoid

“…In contrast, when the metalation was conducted with only n -BuLi, the coupling yield was less than 30% without reproducibility. We believe that this example will broaden the synthetic usefulness of the n -BuLi-Bu 2 Mg-mediated dithiane coupling. , Instead of ortho ester 7 , each dimethyl, diethyl, and di- t -butyl ester was used for this coupling; however, only a complex mixture was obtained.…”

Synthesis of C21‐C41 fragment of the reported structure of Neaumycin B

“…Asymmetric syn ‐aldol reaction of chiral oxazolidinone 8 and aldehyde 9 by Evans protocol proceeded smoothly to furnish the syn ‐aldol product 17 in 85% yield, 12 and treatment of 17 with NH(Me)(OMe)‐HCl in the presence of AlMe 3 provided Weinreb amide 18 in 70% yield. The hydroxy‐group directed epoxidation of allylic alcohol 18 with m ‐CPBA occurred to give epoxide 19 13 . O‐methylation of the secondary hydroxy group in 19 using standard conditions and addition of alkyl lithium species, which was derived from alkyl bromide 21 by lithium‐halogen exchange reaction with t ‐BuLi, to Weinreb amide was accomplished successfully to provide ketone 22 in 55% yield.…”