Synthesis and spectroscopic correlation of the diastereoisomers of 2,3-dihydroxy-2,6,8-trimethyldeca-(4Z,6E)-dienoic acid: implications for the structures of papuamides A–D and mirabamides A–D

Abstract

All 4 diastereomeric possibilities for the 2,3-dihydroxy-2,6,8-trimethyldeca-(4Z,6E)-dienoic acid (Dhtda) residue, found in the cyclic depsipeptide natural products papuamides A-D and mirabamides A-D, were stereoselectively synthesized using a Z-selective Wittig reaction of both enantiomers of 2,4-dimethylhex-2-enyl-triphenylphosphonium bromide with all four diastereoisomers of ethyl-3-formyl-2-methyl-1,4-dioxaspiro[4,4]nonane-2-carboxylate. To elucidate the configuration of Dhtda, the 1H- and 13C-NMR spectra of the synthetic isomers were compared to those of the natural residue. On the basis of that comparison, it is suggested that the likely configuration of the diastereomer present in Dhtda residue is either (2R,3S,8S) or (2S,3R,8S) in the papuamides and mirabimides.

Cover Picture: Reduction of Charge and Discharge Polarization by Cobalt Nanoparticles‐Embedded Carbon Nanofibers for Li–O2 Batteries (ChemSusChem 15/2015)

“…The mixture was warmed to room temperature, the solvent was removed under reduced pressure, and the residue was purified by silica gel column chromatography (petroleum ether/Et 2 O, 97:3) to give ester ( ± )‐ 10 (1826.3 mg, 61 %). The spectroscopic data for compound ( ± )‐ 10 were identical to those described in the literature 18…”

“…The aqueous phase was extracted with CH 2 Cl 2 (3 × 40 mL), and the combined organic extracts were washed, dried with anhydrous sodium sulfate and filtered. Evaporation of the solvent gave a crude residue, which was purified by silica gel column chromatography (petroleum ether/EtOAc, 80:20) to give (2 E ,4 S )‐2,4‐dimethylhex‐2‐en‐1‐ol [( S )‐ 11 ] (400.2 mg, 73 %), whose spectroscopic data were identical to those described in the literature 18…”

“…Commercially available (±)‐2‐methylbutan‐1‐ol was subjected to one‐pot oxidation/olefination using the TEMPO–BAIB [2,2,6,6‐tetramethylpiperidin‐1‐oxyl and bis(acetoxy)iodobenzene] system and (carbethoxyethylidene)triphenylphosphorane17 to give (±)‐( E )‐ethyl 2,4‐dimethylhex‐2‐enoate [(±)‐ 10 ] in 61 % yield 18. Reduction of (±)‐ 10 with DIBAL and subsequent oxidation with PCC produced the corresponding aldehyde [i.e., (±)‐ 9 ] 8.…”

Synthesis of the Azaphilones (+)-Sclerotiorin and (+)-8-O-Methylsclerotiorinamine Utilizing (+)-Sparteine Surrogates in Copper-Mediated Oxidative Dearomatization

“…11 DIBAL-H reduction of 15 provided alcohol 16 (55 %) which was cleanly oxidized with manganese oxide to produce enal 17 . 12 Chlorous chromium-mediated Takai olefination 13 of 17 produced iodo-diene 18 (65 % yield over two steps, 10:1 E:Z selectivity).…”

Aggregation‐Induced Emission of Multiphenyl‐Substituted 1,3‐Butadiene Derivatives: Synthesis, Properties and Application

“…Multiphenyl-substituted1 ,3-butadiene (MPB) and its derivatives are of substantial importance not only due to their presence as key structural units in many naturalp roducts and important pharmaceuticals [41,42] but also due to their great potential in liquid crystals, illuminants, and nonlinear optical materials. [43][44][45][46][47][48] Most of the interest lies in their role as models for conformational properties and photoisomerization reactions involving ap olyene double bond in compounds of biological interest( proteins, vitamin D, visual pigments,e tc.)…”