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A flexible approach to both type II and III lepadin alkaloids is developed for the first time. A key Diels–Alder reaction based on a novel chiral ketolactone dienophile is employed to obtain the desirable all- cis -trisubstituted cyclohexene with excellent regio- and stereoselectivity. As the subsequent closure of the piperidine ring is devised at the N1 and C2 position via an intramolecular nucleophilic amination, the two stereochemical types of lepadin frameworks with the opposite configuration at C2 can be conveniently accessible from a common intermediate. By the approach, lepadins D, E (type II) and F (type III) are stereo-selectively synthesized from ethyl l -lactate. [ABSTRACT FROM AUTHOR]

An efficient approach to the type III lepadin alkaloids (lepadins F and G) has been developed through a key Diels–Alder reaction, in which a novel ketolactone‐type dienophile with chiral diol unit is employed to generate the desirable all‐cis‐trisubstituted cyclohexene with excellent regio‐ and stereoselectivity control. The subsequent selective sulfonylation of the diol unit followed by SN2 cyclization under hydrogenation conditions could construct the substituted piperidine ring. By using this approach, (−)‐lepadin F is synthesized from ethyl l‐lactate for the first time. [ABSTRACT FROM AUTHOR]

Two new synthetic approaches to anhydrogabosines are developed from the polyoxygenated aldol cyclization intermediates, bearing different O‐protecting groups, which were transformed to various gabosine‐type cyclitols. Selective sulfonylation on the required hydroxyl group of the intermediates and the subsequent oxirane ring closure are employed as the key steps in both approaches, by which (+)‐epoxydon, (–)‐phyllostine, (–)‐RKTS 33, and (–)‐parasitenone were synthesized from δ‐d‐gluconolactone. [ABSTRACT FROM AUTHOR]

• The first employment of d -glucono-δ-lactone to synthesize the four styryllactones. • Concise and economical synthetic route. • One-pot construction of the furanofurone bicyclic framework. The concise and efficient synthesis of (+)-goniofufurone, (+)-7- epi -goniofufurone, (+)-crassalactones B and C were achieved in 6 to 7 steps from the known d -glucono-δ-lactone derivative 9. An acid-mediated cascade cyclization was employed to construct the furanofurone bicyclic framework in one-pot. [ABSTRACT FROM AUTHOR]

A new practical synthesis of Pt-650, zalypsis and renieramycin T is achieved by employing a Pictet−Spengler cyclization coupling of the tetrahydroisoquinoline and phenylalaninol partners with good yield and reproducibility, in which both the two coupling partners are prepared by a common route. Moreover, a one-pot Mitsunobu displacement/photolysis sequence of methoxyquinone alcohol intermediate implements the introduction of the amino functionality at C-22 and A-ring modification in one step. By the approach, Pt-650, zalypsis and renieramycin T are synthesized with 21–24 total synthetic steps from N -Cbz- l -tyrosine in good overall yield respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The first total synthesis of zalypsis and the practical synthesis of phthalascidin (Pt-650) are achieved through the Pictet-Spengler cyclization coupling strategy. The direct iodination of the primary alcohol in trihydroxyl intermediate 26 followed by S N 2 reaction with potassium phthalimide is employed to rapidly introduce the required amino functionality at C-22 on the pentacyclic framework. By the approaches, the two antitumor agents can be obtained from sesamol or N -Cbz- l -tyrosine with ca. 8%-10% overall yield. [ABSTRACT FROM AUTHOR]