Takaaki Sato 교수

Nucleophilic addition to amides has been recognized as a promising transformation for total synthesis of complex alkaloids. Amides can accept two different organometallic reagents through the nucleophilic addition, which enables it to serve as a stable surrogate of multi-substituted amines. However, the nucleophilic addition has been overlooked for a long time due to three main reasons: low electrophilicity of amide carbonyls, potential hydrolysis of the reaction intermediate and excess addition

An amide group is one of the most abundant functional groups in organic synthesis. However, nucleophilic addition to amide carbonyls has received less attention than their construction due to their high stability. In this Perspective, we describe our recent progress with N-alkoxyamides. Incorporation of an N-alkoxy group as a reactivity control element into the nitrogen atom of an amide successfully overcomes issues inherent to the nucleophilic addition. The reaction can introduce two different

While the synthesis of amide bonds is now one of the most reliable organic reactions, functionalization of amide carbonyl groups has been a long-standing issue due to their high stability. As an ongoing program aimed at practical transformation of amides, we developed a direct nucleophilic addition to N-alkoxyamides to access multisubstituted amines. The reaction enabled installation of two different functional groups to amide carbonyl groups in one pot. The N-alkoxy group played important roles

Abstract Skipped dienes (1,4‐dienes) are widely distributed in a variety of biologically active natural products. The synthesis of these skipped dienes is a relatively undeveloped area compared with that of conjugated dienes (1,3‐dienes) due to the sp 3 ‐hybridized carbon between two olefins. Especially, development of methods to meet both high stereoselectivity and convergency is highly challenging. This review focuses on recent advances in the synthesis of skipped dienes in the total synthesis

Auf direktem Weg: Sequenzielle nucleophile Additionen an N-Methoxyamide durch DIBAL und Organometallreagentien ergeben substituierte N-Methoxyamine (siehe Schema, DIBAL=Diisobutylaluminiumhydrid). Die über Fünfringchelate verlaufenden Eintopfprozesse eröffnen einen Zugang zu funktionalisierten acyclischen Amiden und Makrolactamen ohne den für reationsträge Amid-Carbonylgruppen sonst nötigen zusätzlichen Aktivierungsschritt. Detailed facts of importance to specialist readers are published as ”Sup

A detailed description of our second-generation total synthesis of salinosporamide A is presented. Three contiguous stereocenters in the γ-lactam structure seen in the natural product were established by stereoselective functionalization of a D-arabinose scaffold, including an Overman rearrangement to generate a highly congested tetrasubstituted carbon center. One of the definitive reactions in the synthesis was a Lewis acid mediated skeletal rearrangement of a pyranose structure, which enabled

The asymmetric total synthesis of fasicularin is reported. The key to success is the use of a chiral N-alkoxyamide to control both reactivity and stereoselectivity. This functional group enables the aza-spirocyclization and the reductive Strecker reaction, which cannot be realized with an ordinary amide. In addition, use of the chiral alkoxy group establishes two consecutive stereocenters in the aza-spirocyclization through remote stereocontrol.

The collective synthesis of pentacyclic stemoamide-type alkaloids is recognized as a daunting task despite high demand for a comprehensive biological profiling of these natural products. In this Letter, we report a unified synthesis of seven pentacyclic alkaloids and two unnatural derivatives. The keys to success are (1) the chemoselective assembly of four five-membered building blocks, (2) the direct oxidation of pyrrolidine natural products to pyrrole derivatives, and (3) the stereodivergent c

Full details of a stereodivergent hydroboration of allenes are reported. While hydroboration of an allene with 9-BBN provided a thermodynamically stable (E)-allylic alcohol after oxidative work-up, the reaction of an identical allene with HB(Sia)₂ (disiamylborane) formed a (Z)-allylic alcohol as the kinetic product. The developed conditions allowed for the synthesis of trisubstituted olefins in a highly stereoselective fashion, which is known to be challenging. The method was also app

Abstract A chemoselective approach for the total synthesis of (±)‐gephyrotoxin has been developed. The key to success was the utilization of N ‐methoxyamides, which enabled the direct coupling of the amide with an aldehyde and selective reductive nucleophilic addition to the amide in the presence of a variety of sensitive and electrophilic functional groups, such as a methyl ester. This chemoselective approach minimized the use of protecting‐group manipulations and redox reactions, which resulte

This article describes the details of two new types of Overman rearrangement from allylic vicinal diols. Starting from identical diols, both bis(imidate)s and cyclic orthoamides were selectively synthesized by simply changing the reaction conditions. Whilst exposure of the bis(imidate)s to thermal conditions initiated the double Overman rearrangement to introduce two identical nitrogen groups in a single operation (the cascade-type Overman rearrangement), the reaction of cyclic orthoamides resul

The enantioselective total synthesis of (–)-stemoamide using Overman/Claisen rearrangement of an allylic 1,2-diol is reported. The enantiopure allylic 1,2-diol was efficiently prepared from naturally occurring dimethyl tartrate. The chirality transfer reactions through two consecutive [3,3]-sigmatropic rearrangements proceeded with complete diastereoselectivity in a one-pot process.

Abstract The full details of a unified total synthesis of madangamine alkaloids are disclosed. Our central strategy is based on the construction of a common ABCE-tetracyclic system, followed by the late-stage installation of various D-rings. The common intermediate is assembled through N-acyliminium cyclization of a propargylsilane, and formation of the (Z,Z)-skipped diene. Stereoselective synthesis of the (Z,Z)-skipped diene is especially challenging, and is accomplished by the combination of Z

Nucleophilic addition to amide carbonyl groups is the simplest way to access multi-substituted amines found in biologically active natural alkaloids and pharmaceuticals. However, this promising transformation has received less attention due to their high stability. In this article, we describe our recent progress with N-alkoxyamides. Incorporation of an alkoxy group as a reactivity control element into the nitrogen atom of an amide successfully overcomes issues inherent to the nucleophilic addit