In most species of social insect the queen signals her presence to her workers via pheromones. Worker responses to queen pheromones include retinue formation around the queen, inhibition of queen cell production and suppression of worker ovary activation. Here we show that the queen signal of the Brazilian stingless bee Friesella schrottkyi is a mixture of cuticular hydrocarbons. Stingless bees are therefore similar to ants, wasps and bumble bees, but differ from honey bees in which the queen's signal mostly comprises volatile compounds originating from the mandibular glands. This shows that cuticular hydrocarbons have independently evolved as the queen's signal across multiple taxa, and that the honey bees are exceptional. We also report the distribution of four active queen-signal compounds by Matrix-assisted laser desorption/ionization (MALDI) imaging. The results indicate a relationship between the behavior of workers towards the queen and the likely site of secretion of the queen's pheromones.
A variety of C-2 and C-5 difunctionalized indolizines have been prepared through the reaction of 1-ester-substituted indolizines with organometallic bases followed by a reaction with different electrophiles. Metalation takes place under mild conditions allowing the isolation of a number of difunctionalized indolizines in good yields. The regioselectivity of the reaction appears to be governed by the nature of the base and electrophile.
A simple protocol for the Pd(OAc)2‐catalyzed cross‐coupling reaction of 1‐benzoyl‐(2S)‐isopropyl‐5‐iodo‐2,3‐dihydro‐4(H)‐pyrimidin‐4‐ones with potassium aryltrifluoroborates was developed. The reaction is performed at 110 °C with a ligand‐free catalyst. In all cases, complete conversion of the 1‐benzoyl‐(2S)‐isopropyl‐5‐iodo‐2,3‐dihydro‐4(H)‐pyrimidin‐4‐onesand aryltrifluoroborates into the C–C coupling products was observed within 30–360 min. It is noteworthy that a largevariety of groups present in the potassium aryltrifluoroborates (–CF3, –OMe, –SEt, –CN, –CHO, –Cl, –Cbz, –NCbz,–OH, –CO2H) could be tolerated. Hydrogenation of the endocyclic double bonds in the Suzuki–Miyaura products followed by acid hydrolysis afforded highly enantioenrichedα‐aryl‐substituted β‐amino acids.
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