A Concise Total Synthesis of (--)-Maoecrystal Z

The first total synthesis of (--)-maoecrystal Z is described. The key steps of the synthesis include a diastereoselective Ti^(III)-mediated reductive epoxide coupling reaction and a diastereoselective Sm^(II)-mediated reductive cascade cyclization reaction. These transformations enabled the preparation of (--)-maoecrystal Z in only 12 steps from (--)-γ-cyclogeraniol

(1R,2R,3R,4R,5S)-2,3-Bis[(2S′)-2-acet­oxy-2-phenyl­acet­oxy]-4-azido-1-[(2,4-dinitro­phen­yl)hydrazono­meth­yl]bicyclo­[3.1.0]hexa­ne

In the title compound, C38H29N7O12, the five-membered ring adopts an envelope conformation in which the ‘flap’ is cis to the cyclo­propane group. This conformation is similar to those of other bicyclo­[3.1.0]hexane analogues for which crystal structures have been reported. The absolute configuration of the stereogenic centers on the cyclo­pentane ring, as determined by comparison with the known configurations of the stereogenic centers in the (2S)-2-acet­oxy-2-phenyl­acet­oxy groups, is 1(R), 2(R), 3(R), 4(R) and 5(S). An intramolecular N—H⋯O hydrogen bond is present

Quantum mechanical considerations on algebraic structure of central molecular chirality

The chiral algebra of tetrahedral molecules, derived from Fischer projections, is discussed in the framework of quantum mechanics. A quantum chiral algebra is obtained whose operators, acting as rotations or inversions, commute with the Hamiltonian of the system. It is shown that energy and chirality eigenstates are strictly related through the Heisenberg relations, while chirality operators conserve parity eigenstates.Comment: 16 page

Catalytic enantioselective synthesis of quaternary carbon stereocentres.

Quaternary carbon stereocentres-carbon atoms to which four distinct carbon substituents are attached-are common features of molecules found in nature. However, before recent advances in chemical catalysis, there were few methods of constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for the synthesis of single stereoisomers of such organic molecules. This progress now makes it possible to incorporate quaternary stereocentres selectively in many organic molecules that are useful in medicine, agriculture and potentially other areas such as flavouring, fragrances and materials

Readily accessible sp3-rich cyclic hydrazine frameworks exploiting nitrogen fluxionality

Increased molecular complexity correlates with improved chances of success in the drug development process. Here, a strategy for the creation of sp3-rich, non-planar heterocyclic scaffolds suitable for drug discovery is described that obviates the need to generate multiple stereogenic centers with independent control. Asymmetric transfer hydrogenation using a tethered Ru-catalyst is used to efficiently produce a range of enantiopure cyclic hydrazine building blocks (up to 99% ee). Iterative C–N functionalization at the two nitrogen atoms of these compounds produces novel hydrazine and hydrazide based chemical libraries. Wide chemical diversification is possible through variation in the hydrazine structure, use of different functionalization chemistries and coupling partners, and controlled engagement of each nitrogen of the hydrazine in turn. Principal Moment of Inertia (PMI) analysis of this small hydrazine library reveals excellent shape diversity and three-dimensionality. NMR and crystallographic studies confirm these frameworks prefer to orient their substituents in three-dimensional space under the control of a single stereogenic center through exploitation of the fluxional behavior of the two nitrogen atoms

Stereoselective Allylic Alkylations of Amino Ketones and Their Application in the Synthesis of Highly Functionalized Piperidines

Chelated ketone enolates are excellent nucleophiles for allylic alkylations. Electron-withdrawing groups on the allyl moiety allow subsequent intramolecular Michael additions giving rise to piperidines with up to five stereogenic centers

Stereoselective synthesis of the naturally occurring 2-pyranone dodoneine

The first total synthesis of the naturally occurring dihydropyranone dodoneine is reported. Asymmetric allylations were used for the stereoselective generation of the two stereogenic centers. The pyranone ring was created by means of a ringclosing metathesi