The E isomer of a [5]cumulene derivative, 2,2, 9,9-tetramethyl-3,8-diphenyldeca-3,4,5,6,7-pentaene (1), which was previously believed to be unisolable owing to very fast E/Z isomerization, was isolated and structurally characterized. The Z isomer was trapped as the transition-metal complex 5, and the molecular structure was determined. DFT calculations and an electrochemical study on 1 are also described.' ASSOCIATED CONTENT b S Supporting Information. Text, figures, tables, and CIF and MOL files giving details of the preparation, spectroscopic data, and CIF files for 1 and 5, spectroscopic data for 6, an NMR study of 1, electrochemical studies of 1, 3, and 4, details of the DFT calculations, and structures of (E)-and (Z)-1. This material is available free of charge via the Internet at http://pubs.acs.org.

Hop (Humulus lupulus) is cultivated to harvest female flowers that lend a deep flavor, aroma, and bitter taste to beer. However, the rest of the plant is burned or land filled as agro-industrial waste. This work upcycles hop stems (HS), which contain 44% cellulose, and demonstrates their suitability as raw materials for the isolation of cellulose nanofibers (CNFs). The Wise method followed by alkaline pretreatment removed lignin and hemicellulose. 2,2,6,6-Tetramethylpiperidine-1-oxyl radical-mediated oxidation fibrillated CNFs from pretreated and non-pretreated HS. A uniform height distribution was inferred from atomic force microscopy, with a median of ∼2 nm for pretreated and non-pretreated HS-derived CNFs. Solid-state nuclear magnetic resonance and X-ray diffraction characterizations indicated that the pretreatment enhanced the purity and crystallinity of the CNFs, though traces of triacylglycerols and calcium oxalate monohydrate remained. The two CNF samples exhibited similar two-step thermal degradation at 255–260 and 300 °C, though less char residue was produced by the pretreated CNFs.

A total synthesis of ent-sedridine is described. The development of a new method for the construction of the C-2 chiral center of the piperidine ring was achieved using a proline-catalyzed Mannich reaction. Reaction of 4-hydroxybutanal and p-anisidine to form an imine and subsequent addition of acetone gave the key chiral aliphatic precursor with high enantioselectivity.Piperidine alkaloids exist widely in nature and many of them have a chiral center at their C-2 position. 1 However, in most cases, the amount of these alkaloids in biological systems is minute and it is therefore important to develop general methods to obtain these compounds, which have possible bioactivity. 2In the course of our study into the synthesis of indole alkaloids, 3 we have found that a proline-catalyzed asymmetric Mannich reaction 4 serves as a highly effective tool for the construction of a chiral center which is crucial for asymmetric synthesis. 5 Based on previous work, we have tried to apply this catalytic system to the synthesis of piperidine alkaloids and have found that a total synthesis of ent-sedridine could be achieved using the proline-catalyzed Mannich reaction as a key step. This paper describes these results.The piperidine alkaloid sedridine was isolated from Sedum acre in 1955, 6 several total syntheses were reported including those by Davis, 7 Murahashi, 8 Hootele, 9 Takahata, 10 and Litter. 11 The first four syntheses use chiral auxiliaries to obtain the chiral product. Litter and coworkers used the only synthesis involving a catalytic asymmetric transformation. In this paper, catalytic hydrogenation of a ketone was adopted as the asymmetric process, the ketoester intermediate was then reduced to the corresponding hydroxyester using Ru-BINAP as the catalyst under H 2 (200 psi). We thought that there were still drawbacks in the previous syntheses, namely the need for equimolar amounts of chiral sources or harsh reaction conditions.We investigated a new method for the construction of the C-2 chiral center of the piperidine ring, using a prolinecatalyzed Mannich reaction. List and co-workers reported a catalytic asymmetric Mannich reaction using imines, which were formed in situ by the reaction of an aromatic aldehyde and an amine, and enamines derived from (S)-proline and methyl ketones to give b-aminoketones in a highly enantioselective manner. 4 The application of the reaction to aldehydes was, however, seldom reported. 12Retrosynthesis for ent-sedridine is shown in Scheme 1. Sedridine (1) was to be obtained from an aliphatic precursor 2 by the Mitsunobu reaction. Compound 2 could be synthesized from the reaction of an imine 3 (formed by the reaction of 4-hydroxybutanal and p-anisidine) with an enamine 4 derived from (S)-proline and acetone.

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