Aiming for the Ideal Synthesis

Catalyst-controlled regio- and stereoselective synthesis of diverse 12H-6,12-methanodibenzo[d,g][1,3]dioxocines

Regio- and stereoselective synthesis of 12H-6,12-methanodibenzo[d,g][1,3]dioxocines has been accomplished by the EDDA and PTSA-catalyzed cascade reactions of resorcinols and 2-hydroxychalcones.

Furans and singlet oxygen – why there is more to come from this powerful partnership

Using the reaction of furans with singlet oxygen as a means to rapidly access huge structural diversity in a green & sustainable way.

Orthogonality in organic, polymer, and supramolecular chemistry: from Merrifield to click chemistry

The concept of orthogonality has been applied to many areas of chemistry, ranging from wave functions to chromatography. But it was Barany and Merrifield's orthogonal protecting group strategy that paved the way for solid phase peptide syntheses, other important classes of biomaterials such as oligosaccharides and oligonucleotides, and ultimately to a term in widespread usage that is focused on chemical reactivity and binding selectivity. The orthogonal protection strategy has been extended to the development of orthogonal activation, and recently the click reaction, for streamlining organic synthesis. The click reaction and its variants are considered orthogonal as the components react together in high yield and in the presence of many other functional groups. Likewise, supramolecular building blocks can also be orthogonal, thereby enabling programmed self-assembly, a superb strategy to create complex architectures. Overall, orthogonal reactions and supramolecular interactions have dramatically improved the syntheses, the preparation of functional materials, and the self-assembly of nanoscale structures.

Photoassisted synthesis of enantiopure alkaloid mimics possessing unprecedented polyheterocyclic cores

Enantiopure alkaloid mimics are synthesized via high yielding intramolecular cycloadditions of photogenerated azaxylylenes tethered to pyrroles, with further growth of molecular complexity via post-photochemical transformations of primary photoproducts. This expeditious access to structurally unprecedented polyheterocyclic cores is being developed in the context of diversity-oriented synthesis, as the modular design allows for rapid "pre-assembly" of diverse photoprecursors from simple building blocks/diversity inputs.

Organocatalytic 1,4-conjugate addition of ascorbic acid to α,β-unsaturated aldehydes: bio-inspired total syntheses of leucodrin, leudrin and proposed structure of dilaspirolactone

The organocatalytic additions of ascorbic acid to various α,β-unsaturated aldehydes via tandem 1,4-conjugate addition/hemiacetalization/hemiketalization were developed, which provided a rapid entry into the 5-5-5 spirodilactone cores of a family of ascorbylated natural products. Based on the described chemistry, total syntheses of leucodrin, leudrin and the proposed structure of dilaspirolactone were achieved.

Direct synthesis of fluorinated heteroarylether bioisosteres

This work delineates a method for the modular synthesis of reagents that are capable of direct incorporation of difluoroalkyl groups onto heterocycles. The scope and generality of this method is exemplified with the difluoroethyl group (along with the introduction of a new reagent for difluoroethylation, DFES-Na) and a proof of principle is shown for a general synthesis of fluorinated heteroarylether bioisosteres.

Aziridinyl imines in organic synthesis: Development of tandem reaction strategies and application to total synthesis of natural products

Aziridinyl imines are well-known carbene equivalents because they are precursors of diazo compounds from which reactive intermediates can be produced. These carbene equivalents can be utilized as zwitterionic species, diradicals, or 4π system for cycloaddition reactions. Thus, the intermediates derived from aziridinyl imines have been used in the sulfur-ylide-mediated epoxide formation, tandem free-radical reactions, or cyclopropanation reaction via carbene intermediates to form trimethylenemethane (TMM) diyls, which undergo [2 + 3] cycloaddition reactions to form cyclopentanoids. Diazo compounds generated from aziridinyl imines also react with allenes to form TMM diyls. This reaction was utilized in tandem cycloaddition reactions of linear substrates to form polyquinanes. These tandem reaction strategies were successfully applied to the total synthesis of various cyclopentanoid natural products.

Alternaric acid: formal synthesis and related studies

A silyl glyoxylate three-component-coupling methodology has been exploited to achieve a formal synthesis, an analogue to an intermediate in a distinct formal synthetic route, and a third (unique) approach to the natural product alternaric acid. Highlighted in this study is the versatility of silyl glyoxylates to engage a variety of nucleophile and electrophile pairs to provide wide latitude in the approach to complex molecule synthesis.

How thiostrepton was made in the laboratory

Thiostrepton, a powerful antibiotic belonging to the thiopeptide class, was synthesized in the laboratory for the first time in 2004 through an arduous campaign involving novel strategies and tactics, scenic detours, and unexpected roadblocks. In this Review the author narrates the long journey to success, not so dissimilar to Odysseus' return voyage to Ithaca, full of adventure, knowledge, and wisdom.

A biomimetic route for construction of the [4+2] and [3+2] core skeletons of dimeric pyrrole-imidazole alkaloids and asymmetric synthesis of ageliferins

The pyrrole-imidazole alkaloids have fascinated chemists for decades because of their unique structures. The high nitrogen and halogen contents and the densely functionalized skeletons make their laboratory synthesis challenging. We describe herein an oxidative method for accessing the core skeletons of two classes of pyrrole-imidazole dimers. This synthetic strategy was inspired by the putative biosynthesis pathways and its development was facilitated by computational studies. Using this method, we have successfully prepared ageliferin, bromoageliferin, and dibromoageliferin in their natural enantiomeric form.

Chemoselective palladium-catalyzed α-allylation of α-boryl aldehydes

Herein we report the development of an α-allylation reaction of α-boryl aldehydes that preserves the carbon-boron bond under Pd(0)/Pd(II) catalysis. A variety of α-boryl aldehydes and allylic alcohols participate in this chemoselective transformation. The α-allylated products were obtained as single regioisomers.

An "aprotic" Tamao oxidation/syn-selective tautomerization reaction for the efficient synthesis of the C1-C9 fragment of fludelone

An efficient synthesis of the C(1)-C(9) fragment of fludelone has been developed. The key step is a tandem silylformylation-crotylsilylation/Tamao oxidation sequence that establishes the C(5) ketone, the C(6), C(7), and C(8) stereocenters, and the C(9) alkene in a single operation from a readily accessed starting material. The stereochemical outcome at C(6) depends critically on the development of an "aprotic" Tamao oxidation, which leads to a reversal in the intrinsic diastereoselectivity observed using "standard" Tamao oxidation conditions.