Evidence of Woodland Management at the Eneolithic Pile Dwellings (3700-2400 BCE) in the Ljubljansko Barje, Slovenia?

It is assumed that people practiced woodland management, i.e., coppicing and pollarding, in prehistory, but details are poorly known.

Evidence for European presence in the Americas in AD 1021.

Transatlantic exploration took place centuries before the crossing of Columbus. Physical evidence for early European presence in the Americas can be found in Newfoundland, Canada. However, it has thus far not been possible to determine when this activity took place.

Development of an enantioselective amine-silver co-catalyzed Conia-ene reaction.

The development of a novel cooperative catalytic system for an amine-silver co-catalyzed Conia-ene reaction of alkyne-tethered C-H-acidic compounds is reported. By using a cost-effective silver salt and a small diamine for the 5-exo-dig-cyclization the cyclopentane products are obtained in very good yields. The enantioselectivity of the reaction could be controlled by exchanging the diamine co-catalyst with a cinchona-derived primary amine.

Asymmetric synthesis of densely functionalized medium-ring carbocycles and lactones through modular assembly and ring-closing metathesis of sulfoximine-substituted trienes and dienynes.

An asymmetric synthesis of densely functionalized 7-11-membered carbocycles and 9-11-membered lactones has been developed. Its key steps are a modular assembly of sulfoximine-substituted C- and O-tethered trienes and C-tethered dienynes and their Ru-catalyzed ring-closing diene and enyne metathesis (RCDEM and RCEYM). The synthesis of the C-tethered trienes and dienynes includes the following steps: 1) hydroxyalkylation of enantiomerically pure titanated allylic sulfoximines with unsaturated aldehydes, 2) α-lithiation of alkenylsulfoximines, 3) alkylation, hydroxy-alkylation, formylation, and acylation of α-lithioalkenylsulfoximines, and 4) addition of Grignard reagents to α-formyl(acyl)alkenylsulfoximines.

Asymmetric modular synthesis of highly functionalized medium-sized carbocycles and lactones via ring-closing metathesis of sulfoximine-substituted trienes.

A modular asymmetric synthesis of medium-sized carbocycles and lactones has been developed that affords highly substituted 7-, 9-, and 11-membered rings. The key steps are (1) the highly diastereoselective synthesis of sulfoximine-substituted homoallylic alcohols from allylic sulfoximines and unsaturated as well as saturated aldehydes, (2) an E-stereoselective alkylation and hydroxyalkylation of sulfoximine-substituted alkenyllithium derivatives, (3) the esterification of sulfoximine-substituted homoallylic alcohols, and (4) the ring-closing metathesis reaction of sulfoximine-substituted trienes with the ruthenium catalyst 8. Two examples for the further synthetic elaboration of the sulfoximine-substituted carbocycles are provided.