Synthese von (+)-Aspicilin mit Bausteinen aus nachwachsenden Rohstoffen

Synthesis of (+)-Aspicilin Using Building Blocks from Renewable Resources The 18-membered lichen macrolide (+)-aspicilin ( 1 ) is easily built up from compounds 14 , 16 , 3 , and 24 following the C₃ + C₇ + C₆ + C₂ = C₁₈ pattern (see Schemes). The synthesis requires 15 steps and gives 1 in 13% overall yield from D -mannose ( 2 ). The latter compound provides the stereogenic centers C(4), C(5), and C(6). The stereogenic center C(17) is supplied by building block 14 (from (?)-(S)-ethyl lactate).     

Sensitisation of the Near‐Infrared Emission of NdIII from the Singlet State of Porphyrins Bearing Four 8‐Hydroxyquinolinylamide Chelates

The α₄ atropoisomer of a tetraaryl porphyrin and its Pd^II complex, both bearing four hydroxyquinolinyl chelating units pre‐organised on the same face of the porphyrin backbone, bind a Nd^III centre thus affording either a mononuclear or a heterobinuclear anionic species, respectively. The near‐infrared emission of the lanthanide centred at 1064 nm is observed upon excitation of the Soret band at 425 nm. Sensitisation proceeds mainly from the singlet state of the porphyrin.     

Carbene—23: Phosphene: [2+2]-und [4 + 2]-cycloaddition von (diphenylmethylen) phenylphosphan-oxid mit α,β-ungesättigten ketonen

The photolysis of 1 produces the carbene 2, which is transformed into the short lived phosphene 4 by phenyl migration. With the α, β-unsaturated ketones 6a–d in a [2+2] cycloaddition 4 yields the 1,2λ⁵-oxaphos-phetanes 7a–d The heterocycles partially undergo a photofragmentation, which produces the olefines 9a–d and the heterocumulene 8. If 4 is generated from 1 under thermal conditions in the presence of 6a–c, formation of four membered rings and fragmentation is observed too; in addition 4 undergoes a [4+2] cycloaddition with the hetero-1, 3-dienes 6a–c, leading to 15a-c. This behaviour corresponds to that of the carbonylanalogue diphenyl-ketene with 6a (formation of CO₂ and 9a via the β-lactone 16 such as of 17).