Zhilong Li

Bio: Zhilong Li is an academic researcher from Hong Kong University of Science and Technology. The author has contributed to research in topics: Total synthesis & Deoxygenation. The author has an hindex of 5, co-authored 8 publications receiving 131 citations. Previous affiliations of Zhilong Li include University of Hong Kong.

Catalytic Environmentally Friendly Protocol for Achmatowicz Rearrangement.

Abstract: The increasing interest in Achmatowicz rearrangement in organic synthesis calls for a more environmentally friendly protocol since the most popular oxidants m-CPBA and NBS produced stoichiometric organic side product (m-chlorobenzoic acid or succinimide). Mechanism-guided analysis enables us to develop a new catalytic method (Oxone/KBr) for AchR in excellent yield with K2SO4 as the only side product, which greatly facilitates the purification. This protocol was integrated with other transformations, leading to a rapid access to the highly functionalized dihydropyranones.

Highly trans‐Selective Arylation of Achmatowicz Rearrangement Products by Reductive γ‐Deoxygenation and Heck–Matsuda Reaction: Asymmetric Total Synthesis of (−)‐Musellarins A–C and Their Analogues

Abstract: Fully functionalized pyranuloses derived from Achmatowicz rearrangement (AR) are versatile building blocks in organic synthesis. However, access to trans-2,6-dihydropyrans from pyranuloses remains underexplored. Herein, we report a new two-step trans arylation of AR products to access 2,6-trans-dihydropyranones. This new trans-arylation method built on numerous plausible, but unsuccessful, direct arylation reactions, including Ferrier-type and Tsuji–Trost-type reactions, was finally enabled by an unprecedented, highly regioselective γ-deoxygenation of AR products by using Zn/HOAc and a diastereoselective Heck–Matsuda coupling. The synthetic utility of the reaction was demonstrated in the first asymmetric total synthesis of (−)-musellarins A–C and 12 analogues in 11–12 steps. The brevity and efficiency of our synthetic route permitted preparation of enantiomerically pure musellarins and analogues (>20 mg) for preliminary cytotoxicity evaluation, which led us to identify two analogues with three-to-six times greater potency than the musellarins as promising new leads.

Asymmetric Total Syntheses of the trans-2-Aryl-6-alkyltetrahydropyrans Diospongin B and Parvistones D and E from a Common Precursor

Abstract: Asymmetric total syntheses of diospongin B and parvistones D and E are reported. Our strategy features a high-yielding three-step reaction sequence: Achmatowicz rearrangement, reductive γ-deoxygenation, and Matsuda–Heck coupling to construct the rare and challenging trans-2-aryl-6-alkyltetrahydropyrans, which serve as common intermediates for the syntheses of diospongin B, and parvistones D and E.

Asymmetric Total Syntheses of (−)-Hedycoropyrans A and B

Abstract: The first and asymmetric total synthesis of (−)-hedycoropyrans A (1) was accomplished in 18 steps with 5.4% overall yield. The key features of our strategy include (1) construction of the unusual trans-2-aryl-6-alkyl tetrahydropyran core via Achmatowicz rearrangement, Zn-mediated reductive deoxygenation, and Heck–Matsuda coupling reaction, and (2) installation of 3,4-anti-dihydroxy from the corresponding 3,4-syn-dihydroxy THP through chemo- and regioselective IBX oxidation and Evans–Saksena reduction. In addition, C2 epimerization of (−)-hedycoropyan A (1) under the acidic condition furnished (−)-hedycoropyan B (2) with 71% yield. This finding might suggest the biogenetic origin of hedycoropyran B.

Divergent Strategy in Natural Product Total Synthesis.

Abstract: The divergent total syntheses of complex natural products from a common intermediate have attracted enormous attention in the chemical community in the past few years because it can improve the efficiency of chemical synthesis. A number of powerful and unified strategies have been developed by emulating the natural biosynthesis or through innovative transformations. This review focuses on the total synthesis of natural products by applying divergent strategies and the literature covering from 2013 to June 2017. On the basis of where the diversity comes from, the examples are grouped into three parts and discussed in detail. In each group, the examples that synthesize natural products belonging to the same subfamily are put together to contrast with one another.

Homogeneous catalysis for the production of low-volume, high-value chemicals from biomass

Abstract: The transition from petroleum to biorenewable sources of carbon to meet our energy and chemical feedstock needs is difficult, in part because these sources are so different, with petroleum being under-functionalized and biomass being over-functionalized relative to commercial chemicals. However, target lists such as the US Department of Energy’s Top 10 have converged efforts to develop the technologies needed to manufacture the most important feedstocks accessible from biorenewables. Less well defined but equally important to the economic viability of an integrated biorefinery are low-volume, high-value product streams, which would help offset the capital costs of a biorefinery. In this Review, we attempt to bring together some of the advances that could fill these niche areas, with a focus on the conversion of cellulosics into chemicals using homogeneous catalysis. The products range from high-value jet fuels to monomers for high-performance polymers and materials to pharmaceutical intermediates and cover a broad range of structural complexities. A move away from fossil fuels as an energy source will also require a move to new sources for important chemical feedstocks. This Review considers the use of homogeneous catalysis to convert cellulosics into low-volume, high-value chemicals that are currently derived from crude oil.

The Modern Face of Synthetic Heterocyclic Chemistry

Abstract: The synthesis of heterocycles is arguably one of the oldest and at the same time one of the youngest disciplines of organic chemistry. Groundbreaking principles to form heterocycles, mainly by condensation reactions, were recognized in the beginning of the 19th century, and many of the classical reactions discovered at that time are still of great value today. In the 21st century, the wealth of synthetic methodology toward heterocycles is overwhelming, and catalysis, in particular, as one of the cornerstones of green and sustainable chemistry has contributed in a major way to these developments. This perspective tries the impossible by discussing some recent advances in the construction of heterocycles, focusing on catalytic methodology. We are aware that we do not come close to giving adequate credit to the great creativity of chemists in the field.

Achmatowicz reaction and its application in the syntheses of bioactive molecules

Abstract: Substituted pyranones and tetrahydropyrans are structural subunits of many bioactive natural products. Considerable effort is devoted toward the chemical synthesis of these natural products due to their therapeutic potential as well as low natural abundance. These embedded pyranones and tetrahydropyran structural motifs have been the subject of synthetic interest over the years. While there are methods available for the synthesis of these subunits, there are issues related to regio- and stereochemical outcomes, as well as versatility and compatibility of reaction conditions and functional group tolerance. The Achmatowicz reaction, an oxidative ring enlargement of a furyl alcohol, was developed in the 1970s. The reaction provides a unique entry to a variety of pyranone derivatives from functionalized furanyl alcohols. These pyranones provide convenient access to substituted tetrahydropyran derivatives. This review outlines general approaches to the synthesis of tetrahydropyrans, covering general mechanistic aspects of the Achmatowicz reaction or rearrangement with an overview of the reagents utilized for the Achmatowicz reaction. The review then focuses on the synthesis of functionalized tetrahydropyrans and pyranones and their applications in the synthesis of natural products and medicinal agents.