Stereoselective synthesis of novel tetrahydroxypyrrolizidines

Nitrogen-bridgehead compounds: overview, synthesis, and outlook on applications

The nitrogen-bridgehead is a common structural motif present in a multitude of natural products. As many of these abundant compounds exhibit biological activities, e.g. against cancer or bacteria, these derivatives are of high interest. While natural products are often associated with problematic characteristics, such as elaborate separation processes, high molecular complexity and limited room for derivatization, purely synthetic approaches can overcome these challenges. Many synthetic procedures have been reported for preparation of artificial nitrogen bridgehead compounds, however, to our surprise only a fraction of these has been tested for their bioactivity. This review is therefore meant to give an overview of existing synthetic methods that provide scaffolds containing bridgehead nitrogen atoms, covering the period from 2000 to 2023. Reviews which cover subunits of this topic are referenced as well.

Identification of a Unique Resorcylic Acid Lactone Derivative That Targets Both Lymphangiogenesis and Angiogenesis

We synthesized 11 novel L-783277 derivatives, in which a structure rigidifying phenyl ring is incorporated into the 14-membered chiral resorcylic acid lactone system. The SAR study with these substances demonstrated that 17 possesses excellent kinase selectivity against a panel of 335 kinases in contrast to L-783277 and inhibits VEGFR3, VEGFR2, and FLT3 with single-digit nanomolar IC₅₀ values. Also, we found that 21, a stereoisomer of 17, has excellent potency (IC₅₀ = 9 nM) against VEGFR3 and selectivity over VEGFR2 and FLT3. 17, a potent dual VEGFR3 and VEGFR2 inhibitor, effectively suppresses both lymphangiogenesis and angiogenesis in a 3D-microfluidic tumor lymphangiogenesis assay and in vivo corneal assay while SAR131675 blocks only lymphangiogenesis. In addition, 17 blocks the endothelial tube formation and suppresses proliferation of PHE tumor vascular model. 17 will be a valuable templatefor developing therapeutically active and selective substances that target both lymphangiogenesis and angiogenesis.

Pyrrolizidine alkaloids

This review covers pyrrolizidine alkaloids isolated from natural sources. Topics include: aspects of structure, isolation, and biological/pharmacological studies; total syntheses of necic acids, necine bases and closely-related non-natural analogues.

Stereoselective synthesis and glycosidase inhibitory activity of 3,4-dihydroxy-pyrrolidin-2-one, 3,4-dihydroxy-piperidin-2-one and 1,2-dihydroxy-pyrrolizidin-3-one

3,4-Dihydroxy-pyrrolidin-2-one, 3,4-dihydroxy-piperidin-2-one and 1,2-dihydroxy-pyrrolizidin-3-one have been synthesized, using a simple strategy based on the asymmetric dihydroxylation of vinylogous aminoesters and subsequent mild intramolecular cyclization. All these compounds show a partial inhibition of alpha-glucosidase, but were inactive towards other glycosidases.