Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement.

An enantioselective aza-Piancatelli rearrangement has been developed using a chiral Brønsted acid based on pentacarboxycyclopentadiene (PCCP). This reaction provides rapid access to valuable chiral 4-amino-2-cyclopentenone building blocks from readily available starting material and is operationally simple

Synthesis of Optically Active Bifunctional Building Blocks through Enantioselective Copper-Catalyzed Allylic Alkylation Using Grignard Reagents

Enantioselective copper-catalyzed allylic alkylations were performed on allylic bromides with a protected hydroxyl or amine functional group using several Grignard reagents and Taniaphos L1 as a ligand. The terminal olefin moiety in the products was transformed into various functional groups without racemization, providing facile access to a variety of versatile bifunctional chiral building blocks.

Transferring Axial Molecular Chirality Through a Sequence of On-Surface Reactions

Fine management of chiral processes on solid surfaces has progressed over the years, yet still faces the need for the controlled and selective production of advanced chiral materials. Here, we report on the use of enantiomerically enriched molecular building blocks to demonstrate the transmission of their intrinsic chirality along a sequence of on-surface reactions. Triggered by thermal annealing, the on-surface reac-tions induced in this experiment involve firstly the coupling of the chiral reactants into chiral polymers and subsequently their transformation into planar prochiral graphene nanoribbons. Our study reveals that the axial chirality of the reactant is not only transferred to the polymers, but also to the planar chirality of the graphene nanoribbon end products. Such chirality transfer consequently allows, starting from ad-equate enantioenriched reactants, for the controlled production of chiral and prochiral organic nanoarchi-tectures with pre-defined handedness

Baryon chiral perturbation theory with virtual photons and leptons

We construct the general pion-nucleon SU(2) Lagrangian including both virtual photons and leptons for relativistic baryon chiral perturbation theory up to fourth order. We include the light leptons as explicit dynamical degrees of freedom by introducing new building blocks which represent these leptons.Comment: 11 page

VCD helps others in molecular aggregates

Molecular self-assembly is the driving force of a great number of physical, chemical and biological processes in Nature.1 The properties of the molecular aggregates are markedly dependent on the intermolecular forces which hold together the building blocks, but also on the chemical and structural features of these building blocks. The transference of properties from the individual molecules to the bulk aggregate can be summarized in three main behaviours: disappearance (dipole moment), direct sum (weight) and enhancement (resilience). A nice example of the last group is the optical activity. The presence of a chiral seed in the molecules modulates their folding by favouring one among the available macrostructures. As a consequence, new forms of supramolecular chirality are triggered, such as helical, spiral or chiral sheets, which usually give rise to a noticeable increasing of the chiral signal of the aggregates. Vibrational circular dichroism (VCD) is the chiral version of infrared spectroscopy. It combines the intramolecular view provided by the molecular vibrations with the selective capability of a chiral analysis. It is also a suitable technique to observe the aggregation-induced signal enhancement in any type of condensed phase (solid, liquid, gel, etc). Here we present a series of studies on supramolecular systems, Figure 1, in which VCD helps and improves the analysis obtained by other techniques of chiral analysis as electron microscopy (SEM, AFM), electronic circular dichroism (ECD), Raman optical activity (ROA) or circularly polarized luminescence (CPL). These studies are aimed to obtain structural information of the macromolecular scaffolding useful to control the features and applications of the aggregates.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tec

Iridium-Catalyzed Asymmetric Intramolecular Allylic Amidation:Enantioselective Synthesis of Chiral Tetrahydroisoquinolines and Saturated Nitrogen Heterocycles

For the first time iridium catalysis has been used for the synthesis of chiral tetrahydroisoquinolines with excellent yields and high enantioselectivities (see scheme; cod=1,5-cyclooctadiene, DBU=1,8-diazabicyclo[5.4.0]undec-7-ene). These products are important chiral building blocks for the synthesis of biologically active compounds, in particular alkaloids

Synthesis and Its Application to the Synthesis of Biologically Active Natural Products of New and Versatile Chiral Building Blocks

This article describes a design and synthesis of new and versatile chiral building blocks and its application to the biologically active natural product synthesis. The chiral building blocks were prepared using a biocatalysis in an enantiomerically pure state. As an application of the above chiral building blocks to the synthesis of biologically active natural product, we demonstrated the diastereodivergent synthesis of the 3-piperidinol alkaloids cassine, spectaline, prosafrinine, iso-6-cassine, prosophylline, prosopinine, and also established the flexible route to the 5,8-disubstituted indolizidine or 1,4-disubstituted quinolizidine type of Dendrobates alkaloids. As another application to the synthesis of biologically active alkaloids, we accomplished the first enantioselective total synthesis of marine alkaloids clavepictines A, B, and pictamine using a highly stereoselective Michael type quinolizidine ring closure reaction as the crucial step, and the first total synthesis of a marine alkaloid lepadin B was also achieved using aldol cyclization controlled by a A(1,3) strain.本総説は，平成12年度日本薬学会北陸支部学術奨励賞の受賞を記念して記述したものである

Mapping 6D N = 1 supergravities to F-theory

We develop a systematic framework for realizing general anomaly-free chiral 6D supergravity theories in F-theory. We focus on 6D (1, 0) models with one tensor multiplet whose gauge group is a product of simple factors (modulo a finite abelian group) with matter in arbitrary representations. Such theories can be decomposed into blocks associated with the simple factors in the gauge group; each block depends only on the group factor and the matter charged under it. All 6D chiral supergravity models can be constructed by gluing such blocks together in accordance with constraints from anomalies. Associating a geometric structure to each block gives a dictionary for translating a supergravity model into a set of topological data for an F-theory construction. We construct the dictionary of F-theory divisors explicitly for some simple gauge group factors and associated matter representations. Using these building blocks we analyze a variety of models. We identify some 6D supergravity models which do not map to integral F-theory divisors, possibly indicating quantum inconsistency of these 6D theories.Comment: 37 pages, no figures; v2: references added, minor typos corrected; v3: minor corrections to DOF counting in section