Opening a New Series of Calcium Boridecarbides with Heterographene Nets by Ca1–x(B,C)6 and Ca1–x(B,C)8 – Two Members of the (CaB2)Cn Compound Series

Ca_1–xB₂C₄ (x ~ 0.08) and Ca_1–xB₂C₆ (x ~ 0.04) are two compounds containing heterographene‐B,C nets which were prepared by solid state synthesis and structurally characterized by X‐ray powder diffraction data. Both compounds crystallize in the space group P6/ mmm (No. 191). The lattice constants are a = 4.55971(5) Å and c = 4.4020(1) Å for CaB₂C₄ and a = 2.58390(5) Å, c = 4.43597(8) Å for CaB₂C₆. The calcium atoms are intercalated between the heterographene (B,C) nets. The calcium atom distribution in Ca_1–xB₂C₆ is disordered, leading to diffuse scattering. A model for this disorder was developed that matches well the observed diffuse scattering observed in the electron diffraction pattern. For Ca_1–xB₂C₆ and its decomposition products magnetic and electric properties are being reported.     

Syntheses of the Macrocyclic Spermine Alkaloids (±)‐Budmunchiamine A – C

The syntheses of four macrocyclic spermine alkaloids, (±)‐budmunchiamine A – C ( 1a – c ) and (±)‐budmunchiamine L4 ( 1 ), were accomplished by Michael addition of spermine to the α,β‐unsaturated esters 3a – d , followed by cyclization of the resulting α,ω‐tetraamino esters 4a – d with triethoxyantimony; N‐methylation of the amino lactams 6a – c yielded the budmunchiamines A – C ( 1a – c ).     

1H and 13C NMR study of phosphopeptides: 2—Ac–PSer–Gly,Ala–PSer–Gly and Gly–PSer–Phe

¹H and ¹³C NMR spectra of AC–PSer–Gly, Ala–PSer–Gly and Gly–PSer–Phe have been measured and analysed as a function of pD. The NMR parameters of the PSeryl side chain are a function of the sequence. The second titration step of the phosphate group (pK₂ = 5.7) is much more difficult to detect in Ac–PSer–Gly and Ala–PSer–Gly than in Gly–PSer–Phe. The conformation in which H-α? C-α? C-β? O? P forms a planar W-type arrangement predominates only for Ala–PSer–Gly. In the other two phosphopeptides the gauche conformations contribute increasingly, in particular for Gly–PSer–Phe.     

Irciformonins E – K,C22‐Trinorsesterterpenoids from the Sponge Ircinia formosana

Chemical investigation of the sponge Ircinia formosana resulted in the isolation of seven new linear C₂₂‐sesterterpenoids, irciformonins E–K ( 1 – 7 ) in addition to irciformonin A ( 8 ), a previously isolated furanosesterterpenoid (=a furan‐moiety‐containing sesterterpenoid) from the same species. The structures were determined by interpretation of HR‐ESI‐MS and 2D‐NMR spectra. The structure of irciformonin A ( 8 ) was revised. Compound 5 exhibited significant inhibition of peripheral blood mononuclear cell proliferation induced by phytohemaglutinin.     

Total Synthesis of the 7,10‐Epimer of the Proposed Structure of Amphidinolide N,Part I: Synthesis of the C1–C13 Subunit

Amphidinolide N, the structure of which has been recently revised, is a 26‐membered macrolide featuring allyl epoxide and tetrahydropyran moieties with 13 chiral centers. Due to its challenging structure and extraordinary potent cytotoxicity, amphidinolide N is a highly attractive target of total synthesis. During our total synthesis studies of the 7,10‐epimer of the proposed structure of amphidinolide N, we have synthesized the C1–C13 subunit enantio‐ and diastereoselectively. Key reactions include an l ‐proline catalyzed enantioselective intramolecular aldol reaction, Evans aldol reaction, Sharpless asymmetric epoxidation and Tamao–Fleming oxidation. To aid late‐stage manipulations, we also developed the 4‐(N‐benzyloxycarbonyl‐N‐methylamino)butyryl group as a novel ester protective group for the C9 alcohol.     

LaMn11C2–x und PrMn11C2–x,Carbide mit gefüllter BaCd11-Struktur

LaMn₁₁C_2–x and PrMn₁₁C_2–x, Carbides with Filled BaCd₁₁ Structure The new compounds LaMn₁₁C_2–x and PrMn₁₁C_2–x were obtained by reaction of the elements in a high-frequency furnace with subsequent annealing. The compounds crystallize tetragonal, space group I4₁/amd, with Z = 4 formula units per cell. The lattice constants are a = 10.4134(4) Å, c = 6.7293(4) Å for LaMn₁₁C_2–x and a = 10.372(1) Å, c = 6.715(1) Å for PrMn₁₁C_2–x. The structure of LaMn₁₁C_2–x was determined from single-crystal diffractometer data and refined to a residual of R = 0.013 for 24 variables and 503 structure factors. The positions of the metal atoms correspond to those of BaCd₁₁. The carbon atoms fill octahedral voids formed by four Mn and two La atoms with an occupancy of 76 ± 1%. This corresponds to the formula LaMn₁₁C_1.52. The structure and chemical bonding of the compound are discussed.     

Synthesis,Isolation and Structures of Trifluoromethylated Fullerenes D2‐C76, C76(1)(CF3)10–18

High‐temperature trifluoromethylation of fullerene C₇₆ chlorination products followed by HPLC separation of C₇₆(CF₃)_n derivatives resulted in the isolation and X‐ray structural characterization of thirteen C₇₆(1)(CF₃)_n compounds including nine new isomers such as one isomer of C₇₆(1)(CF₃)₁₀, two C₇₆(1)(CF₃)₁₂, three C₇₆(1)(CF₃)₁₄, one C₇₆(1)(CF₃)₁₆, and two isomers of C₇₆(1)(CF₃)₁₈. Depending on their addition patterns, C₇₆(1)(CF₃)_n isomers are divided into three subgroups and discussed in terms of trifluoromethylation pathways and relative formation energies.     

Dapholidins A – C,New Isomeric Biisoflavonoids From Daphne oleoides

Three new isomeric biisoflavonoids, dapholidins A–C ( 1 – 3 , resp.), have been isolated from the AcOEt‐soluble fraction of the MeOH‐soluble extract of the roots of Daphne oleoides, along with the known compounds daphwazirin ( 4 ), daphnetin 8‐O‐β‐D ‐glucopyranoside ( 5 ), daphnin ( 6 ), daphneticin 4″‐O‐β‐D ‐glucopyranoside ( 7 ), and 6,7‐dihydroxy‐3‐methoxy‐8‐[2‐oxo‐2H‐1‐benzopyran‐7‐(O‐β‐D ‐glucopyranosyl)‐8‐yl]‐2H‐1‐benzopyran‐2‐one ( 8 ). The structures of the new compounds were determined by spectroscopic analyses, including 1D‐ and 2D‐NMR.     

Two phosphonodehydrotripeptides: Boc0–Gly1–Δ(Z)Phe2–α‐Abu3PO3Me2 and Boc0–Gly1–Δ(Z)Phe2–α‐Nva3PO3Et2

The present paper reports the crystal structures of two short phosphonotripeptides (one in two crystal forms) containing one ΔPhe (dehydrophenylalanine) residue, namely dimethyl (3‐{[tert‐butoxycarbonylglycyl‐α,β‐(Z)‐dehydrophenylalanyl]amino}propyl)phosphonate, Boc⁰–Gly¹–Δ(Z)Phe²–α‐Abu³PO₃Me₂, C₂₁H₃₂N₃O₇P, (I), and diethyl (4‐{[tert‐butoxycarbonylglycyl‐α,β‐(Z)‐dehydrophenylalanyl]amino}butyl)phosphonate, Boc⁰–Gly¹–Δ(Z)Phe²–α‐Nva³PO₃Et₂, as the propan‐2‐ol monosolvate 0.122‐hydrate, C₂₄H₃₈N₃O₇P·C₃H₈O·0.122H₂O, (II), and the ethanol monosolvate 0.076‐hydrate, C₂₄H₃₈N₃O₇P·C₂H₆O·0.076H₂O, (III). The crystals of (II) and (III) are isomorphous but differ in the type of solvent. The phosphono group is linked directly to the last C_α atom in the main chain for all three peptides. All the amino acids are trans linked in the main chains. The crystal structures exhibit no intramolecular hydrogen bonds and are stabilized by intermolecular hydrogen bonds only.     

Stereoselective Synthesis of the C(1) – C(28) Fragment of Amphidinol 3

A stereoselective synthesis of the polyol side chain (C(1) – C(28)) of amphidinol 3 has been accomplished following Sharpless epoxidation, Crimmins aldol reaction, Jacobsen kinetic resolution, Sharpless asymmetric dihydroxylation, and our own reaction for the synthesis of a chiral allylic alcohol from an epoxy alcohol. The olefin functionality was introduced by a cross metathesis and Julia–Kocienski olefination.     

Eremosides A – C,New Iridoid Glucosides from Eremostachys loasifolia

Eremosides A–C ( 1 – 3 ), three new iridoid glucosides, were isolated from the AcOEt‐soluble fraction of the EtOH extract of the whole plant of Eremostachys loasifolia, along with buddlejoside B ( 4 ), 10‐O‐benzoylcatalpol ( 5 ), and pakiside A ( 6 ) reported for the first time from this species. The structures of these compounds were elucidated by spectroscopic data including 2D‐NMR, FAB‐MS, ESI‐MS, as well as by acid and basic hydrolyses.