Formal synthesis of (+)-gliocladin C

An asymmetric synthesis of chiral intermediate 15 for (+)-gliocladin C has been accomplished from N-phthaloyl l-tryptophan methyl ester.     

Formal synthesis of (+)-crocacin C

The formal synthesis of (+)-crocacin C is reported. The approach described takes advantage of a highly regioselective epoxide cuprate addition and a diastereoselective Overman rearrangement. The synthesis is practical and amenable to scale up.     

Formal synthesis of schulzeines B and C

A formal synthesis of schulzeines B and C, marine natural products with inhibitory effect against α-glucosidase, has been achieved. The key reactions of the synthesis are N-acyliminium ion cyclization, Sharpless asymmetric dihydroxylation, olefin cross metathesis, and asymmetric allylboration.     

Formal synthesis of dysiherbaine

A formal synthesis of dysiherbaine was achieved from d-mannitol using Grignard addition on chiral imine, RCM and Michael addition as key steps.     

Formal synthesis of cortistatins

A unified strategy toward the asymmetric facile construction of the [6.7.6.5]oxapentacyclic skeleton of cortistatins is reported, featuring intramolecular Diels-Alder (IMDA), oxidative dearomatization, and an oxy-Michael addition reaction.     

Formal total synthesis of borrelidin: synthesis of C1-C11 fragment via desymmetrization strategy

A stereoselective formal total synthesis of borrelidin is described. The synthetic strategy for synthesis of C1-C11 fragment features desymmetrization of Diels-Alder adduct, Sharpless asymmetric epoxidation, regioselective opening of chiral epoxide, and alkylation using Evans chiral auxiliary.     

Formal total synthesis of fostriecin

[reaction: see text] Addition of magnesium anion 4 (M = MgBr, R(1) = TES) to ketone 6 (R(2) = PMB) at -78 degrees C in THF proceeded under chelation control to provide alcohol 7, which possesses the full set of the chiral centers of fostriecin. Subsequently, 7 was transformed successfully to the known key intermediate 2.     

Formal synthesis of semiaquilegin A

A formal synthesis of semiaquilegin A is achieved starting from readily available oridonin in 19 linear steps. The absolute configuration of the natural product has been established. A variety of useful analogues were prepared through this synthetic route.     

Formal total synthesis of neopeltolide

A concise synthesis of the core structure of the macrolide neopeltolide was developed featuring a Prins cyclization to fashion the pyran ring. Key steps in the synthesis of aldehyde 16 were a Leighton allylation and a Feringa-Minnaard asymmetric methyl cuprate addition to an unsaturated thioester. For lactonization, a classical Yamaguchi macrolactonization was used. The longest linear sequence consists of 17 steps providing lactone 26 with an overall yield of 23%.     

Formal total synthesis of triptolide

A new approach to the medicinally-important natural product triptolide is significantly shorter than previous syntheses, highly convergent and avoids the use of protecting groups; key features include two Diels-Alder reactions and a new deoxygenative aromatisation process.     

Formal synthesis of tirandamycin B

A formal synthesis of tirandamycin B is described. The key intermediate is synthesized by Marshall allenyl zinc method, litiofuran coupling, and Achmatowicz reaction to construct the bicyclic core of tirandamycin B.     

Formal synthesis of amphidinin B

An efficient, convergent, and highly stereoselective formal synthesis of amphidinin B (1) is reported herein. In Amphidinin B both C10–C21 (4) and C1–C9 (5) fragments were derived from geraniol 6 and mono-PMB ether of 1,4-butane diol 7 in 19 and 9 steps, respectively. The key steps involved in this synthesis are Sharpless asymmetric epoxidation, Evans aldol, Julia olefination, oxa-Michael, Keck allylation, Mannich reaction, Evans asymmetric alkylation, and Yamaguchi esterification.     

Formal synthesis of herbarumin III

An enantioselective synthesis of herbarumin III is described employing Jacobsen’s hydrolytic kinetic resolution and Sharpless asymmetric dihydroxylation as the key steps.     

Formal synthesis of (+)-discodermolide

[structure: see text] Herein we report the formal total synthesis of (+)-discodermolide in 21 steps (longest linear sequence) from commercially available Roche ester. This synthesis features the assembly of C(9-18) and C(19-24) fragments via a metal-chelated aldol coupling reaction.     

Stereoselectivity in a nitroso-ene cyclization: Formal synthesis of rac-manzacidins A and C

Nitroso-ene (NE) reactions have been adapted in the construction of nitrogen-containing motifs in many biologically interesting compounds. The transient and highly reactive “nitroso” species remains a challenge for designing stereocontrolled syntheses. Although chiral auxiliary-based method has been developed to achieve high diastereoselectivity, the use of the inherent chirality of the nitroso compound for stereochemical control remains underdeveloped. We chose the formation of a γ-lactam via a NE cyclization as a basis to study the applicable principles for future asymmetric syntheses. The selected examples presented herein reveal that the intramolecular hydrogen bond would provide conformational restraint to facilitate excellent facial selectivity in the NE reaction via a chair-like transition state. The sterically bulky amino group also provides excellent stereochemical control possibly through steric repulsion. The following transformations led to a key intermediate (Ohfune's lactone) in the preparation of manzacidins A and C and thus constitutes a formal synthesis.