Microwave-assisted solid-phase organic synthesis (MASPOS) has been demonstrated to significantly facilitate the Cu(II)-or Pd(II)-mediated ring closure of the resin-bound 2-alkynylanilides. Under microwave irradiation at 200℃ [for Cu(OAc)2, NMP] or 160℃ [for Pd(MeCN)2Cl2, THF] for 10min, 1-acyl-2-alkyl-5-arenesulfamoylindoles were obtained, after cleavage from the resin, in 95-99% purities and in 65-82% overall yields via a 5-step synthetic sequence.

Cyclodeca-1,5-diyn-3-ene, the parent core of naturally occurring 10-membered ring enediyne antitumor antibiotics, decomposes at 37℃ with a t1/2 value of 18h. A prodrug approach was envisaged by in situ formation of the core structure via rearrangement of an allylic double bond. Three synthetic methods including intramolecular lithium acetylide addition to aldehyde, intramolecular Nozaki-Hiyama-Kishi reaction, and intramolecular Sonogashira cross-coupling have been established for synthesis of the enediyne precursors, (E)-3-acyloxy-4-(arylmethylidene) cyclodeca-1,5-diynes. The latter are transformed into 10-membered ring enediynes in the resence of a catalytic amount of Ln(fod)3 under mild reaction conditions. Alternatively, the enediyne precursor dissociates in buffer solution into an allylic cation or a quinone methide intermediate, which reacts with a nucleophile (such as H2O) to form the bioactive enediyne. LC-MS data confirmed formation of the 10-membered ring enediyne from the precursor, which exhibits DNA cleavage activity and cytotoxicity against P388 cancer cell line.

A novel class of nonbiaryl atropisomeric P,O-ligands possessing an N,N-dialkyl-1-naphthamide skeleton has been synthesized via an efficient chemical resolution process. It represents the first example of axially chiral P,O-ligands devoid of central chirality. Up to 94.7% ee was obtained for the Pd-catalyzed asymmetric allylic lkylation (AAA). Effects of solvent, base, and the bulk of the C8 oxygen group of the P,Oligand on the AAA reaction were examined.

We have discovered a novel class of (E)-3-acyloxy-4-(arylmethylidene)cyclodeca-1,5-diynes which exhibit promising enediyne-like DNA cleavage and cytotoxic activities. LCMS analysis of the incubation mixture (pH 8.5, 37℃) confirmed formation of 10-membered ring enediyne presumably via an allylic cation and suggested that the 1,4-benzenoid diradical might be one of the active species for DNA damage and cytotoxicity.

The naturally occurring enediynes1 represent a novel class of antitumor antibiotics that feature a (Z)-hex-3-ene-1,5-diyne moiety constrained in a 9-or 10-membered ring. Coupled with other structural domains responsible for drug activation and delivery, the enediyne antitumor antibiotics present challenging targets for chemical synthesis.1a-c Stimulated by the intriguing mechanism of action and promising biological activity, extensive chemical and biological investigations on enediynes have been carried out during the past decade.1 It is known that cycloaromatization2 of enediynes such as 2 will give the diradical species 3, which can damage DNA through hydrogen atom abstraction from the deoxyribose residue (Scheme 1).1a,d,e,3 This event is regarded as the origin of the biological activity of enediynes. However, the extreme lability of simple 9- or 10-membered ring enediynes presents an obstacle for the development of synthetic enediyne drugs. In our recent work, we have established an efficient methodology for conversion of the thermally stable 1,2-diynyl-substituted allyl alcohols into acyclic enediynes by rearrangement of the allylic double bond.4 A relatively unstrained 11-membered ring enediyne was synthesized similarly.4b Our methodology is conceptually related to the intramolecular allylic rearrangement proposed for the action of artifacts of the maduropeptin chromophore5,6 and represents one of the emerging strategies7 for enediyne prodrug design and synthesis. In this paper, we disclose the synthesis and DNA cleavage activity of the 10-membered ring enediyne