Miaosheng Li

Synthesis of several cleistrioside and cleistetroside natural products via a divergent de novo asymmetric approach.

The de novo asymmetric syntheses of several partially acylated dodecanyl tri- and tetra-rhamnoside natural products (cleistriosides-5 and 6 and cleistetrosides-2 to 7) have been achieved (19-24 steps). The divergent route requires the use of three or less protecting groups. The asymmetry was derived via Noyori reduction of an acylfuran. The rhamno-stereochemistry was installed by a diastereoselective palladium-catalyzed glycosylation, ketone reduction and dihydroxylation.

De Novo Asymmetric Approach to the Disaccharide Portion of SCH-47554

A method for the asymmetric synthesis of the disaccharide portion of SCH-47554 has been developed in 6 steps. The route is shorter than the reported route to a related disaccharide. The route involves the use of the Noyori reduction to establish the asymmetry of the d- and l-sugar portion of the molecule. Diastereoselective Pd-glycosylation reaction and subsequent post-glycosylation transformation are used to establish the remaining stereocenter.

A General Approach to Anionic Acid-Labile Surfactants with Tunable Properties

A general approach to the synthesis of a new series of unique sulfate anionic acid-labile surfactants (AALS) was developed. In this approach, the ketal was derived from methyl pyruvate, and the sulfate motif was introduced via sulfitylation of the alcohol, oxidation, and finally conversion of the sulfate diester to the desired sodium salt. The physicochemical properties in aqueous solution of this novel series of surfactants, such as CMCs, solubility, acid lability, and stability were studied.

Chapter 8 Achmatowicz approach to 5,6-dihydro-2H-pyran-2-one containing natural products

Publisher Summary This chapter discusses the enantioselective synthesis of eight target molecules accomplished by the use of the Achmatowicz reaction. The asymmetry of furan alcohol can be installed by either a sharpless asymmetric dihydroxylation reaction or a Noyori reduction. In all cases, the target molecules are prepared with greater efficiency than previous syntheses, which rely on either chiral starting material or resolution procedures. The latter two routes provide sufficient material for biological testing, with the ultimate route allowing for the rapid preparation of C-5/C-6 analogs. Substituted α,β-unsaturated δ-lactones (5,6-dihydro-2 H -pyran-2-ones) molecules have an α,β-unsaturated δ-lactones moiety A with various substituents (for example, alkyl, alkenyl, aryl, or hydroxyl) at the C-5 and C-6 positions. The numbering of the lactones ring begins with the ring oxygen and proceeds clockwise around the ring, with substituents at the C-6 and C-5 positions differentiated using prime and double prime numbers, respectively. The biological diversity of these natural products ranges from plant growth inhibition, cytotoxicity against tumor cells, and antifungal or antimicrobial activity.