Asymmetric synthesis using organosulfur and organoselenium compounds has been extensively studied since the discovery of Andersen synthesis of chiral sulfoxides and the first isolation of chiral selenoxides, respectively. Recent advances in this field were reviewed in the following three topics; 1) synthesis of chiral sulfoxides, 2) synthesis of chiral selenoxides, 3) asymmetric induction via chiral selenoxides.
This review describes the recent studies on spontaneous condensation of amphiphilic amino acid esters in ordered molecular assemblies. The rate of polycondensation in the monolayers is dependent on the pKa value of the conjugated alcohol released from ester group. Lateral progress of the spontaneous condensation and resultant morphologies of peptide monolayers was observed by scanning electron microscopy (SEM) with the transferred monolayers on a Si wafer. The morphological uniformity of the resultant monolayers was affected by the chirality of the head group of the amphiphilic esters. Formation of the peptide liposomes by spontaneous condensation in the bilayers is also described.
Brevetoxins are powerful neurotoxins produced by dinoflagellate strain Gymnodinium berve Davis, isolated from the Florida “red tide” dinoflagellate. Their unique structure presents an opportunistic and formidable synthetic problem, particularly with regard to the construction of its medium-sized ring systems. This would almost certainly require new synthetic technology and a carefully designed strategy before yielding to total synthesis. This review deals with some new, practical and efficient synthetic technologies for the construction and chemical manipulation of medium-sized cyclic ether developed in K K.C. Nicolaou's laboratories. First total synthesis of hemibrevetoxin B (3) performed by these technologies is also delineated.
Synthesis of trichlorinated γ-lactones or γ-lactams from allyl trichloroacetates or N-allyl trichloroacetamides was achieved by transition metal-catalyzed radical cyclizations. Treatment of these trichlorinated starting materials with a catalytic amount of cuprous salts or a ruthenium-phosphine complex resulted in cleavage of a carbon-chlorine bond and subsequent intramolecular addition of the carbon moiety and the chlorine atom to the carbon- carbon double bond. Stereochemistry of the product was similar to that observed in free radical cyclizations ; e.g. stereochemistry of β- and γ-substituents generated by the cyclization of 1-methyl-2-propenyl trichloroacetate was predominantly trans, whereas a cis-fuzed bicyclic lactone was formed by the reaction of 2-cyclohexenyl trichloroacetate. The cyclization of N-allyl trichloroacetamides offers a facile preparative method for pyrrolidinone derivatives from easily available allylic alcohols by the combination with the [3.3] -sigmatropic rearrangement of allyl trichloroimidates. It also provides an interesting entry to alkaloid skeletons. In the cyclization of N-substituted N-allyl trichloroacetamides, judicious choice of the N-substituent and the catalyst dramatically lowered the reaction temperature, and enabled very efficient stereocontrol.
This article deals with our recent results on the investigation of the reaction and synthetic application of trialkyl 2-indolylborate. (1) High regioselectivity on the reaction of the indolylborate with electrophiles in the presence of copper (I) ion, highly depending on the nature of electrophiles used, was found. (2) Synthetic application of an intramolecular alkyl migration process in the indolylborate for the construction of cyclo [1, 2-a] and cyclo [1, 2-b] indole systems was realized via an intramolecular cyclization process. (3) Palladium catalyzed cross coupling, carbonylative cross coupling and tandem cyclization cross coupling reactions with the indolylborate were developed and used for the preparation of indole derivatives.
Recent advances in large carbon cluster chemistry (fullerenes) with curved molecular surfaces on sp2 carbon lattices have aroused a large interest in the field of nonplanar polycyclic aromatic compounds with circular arrangement of benzene rings known as circulene. The nonplanar circulenes featuring a structural motif present in carbon clusters were prepared and their rather unusual physical and chemical properties resulting from their strained and nonplanar structure were reported.