STATEMENT OF PROBLEM The use of metal clasps on anterior teeth may cause esthetic problems. Recently, acetal resins have been used as an alternative tooth-colored denture clasp material to improve esthetics. However, there are few studies to support acetal resin use. PURPOSE The purpose of this in vitro study was to compare the retentive force and deformation of acetal resin and cobalt-chromi...

A panel of acid-labile bis-norbornene cross-linkers was synthesized and evaluated for the formation of acid-degradable brush-arm star polymers (BASPs) via the brush-first ring-opening metathesis polymerization (ROMP) method. An acetal-based cross-linker was identified that, when employed in conjunction with a poly(ethylene glycol) (PEG) macromonomer, provided highly controlled BASP formation re...

The reaction of trifluoroacetaldehyde N,O-acetal derivatives with 2 molar equivalents of alkyllithium reagents proceeded viabeta-elimination of fluoride followed by alkyl transfer from excess alkyllithium to the generated ketene N,O-acetal intermediate at the beta-carbon of fluorine groups.

Feulgen and Rossenbeck (1) demonstrated in 1924 in the cytoplasm of cells the presence of substances which give histochemically a color reaction with Schiff’s aldehyde reagent. Feulgen and Voit (2) at the same time showed that the aldehyde group of these substances is not free, but bound in a labile form. The authors called this substance plasmalogen. Feulgen and Bersin (3) succeeded in 1939 in...

The synthesis of the uncommon dihydropyrazinone ring was accomplished by a two-step one pot process taking advantage of the ring rearrangement of N-acylated morpholine acetal derived from serine under acidic treatment in the presence of 2,6-lutidine. The mechanism involves an N-acyl iminium intermediate resulting from morpholine acetal ring opening, which occurs after a nucleophilic attack of t...

Erythromycin A 11,12-methylene acetal (5) and the corresponding 9-methoxime, 9-dihydro, and 8-hydroxy derivatives have been prepared and their antibacterial activities compared with those of erythromycin A and its 11,12-cyclic carbonate. The simple methylene acetal 5 showed excellent activity against Gram-positive organisms in vitro.

Synthesis of monoterpene indole alkaloids, leuconoxine, leuconodine B, and rhazinilam, by transformation melodinine E via 6-hydro-21-dehydroxyleuconolam was established. The pivotal intermediate, 6-hydro-21-dehydroxyleuconolam, prepared from a ring-opening N,S-acetal formation the diaza[5.5.6.6]fenestrane skeleton subsequent chemoselective reduction. These results demonstrate that 6-hydro-21-de...

The facile deprotection of methylene acetal protection of diols under mild conditions is established. The combination of trimethylsilyl triflate (TMSOTf) and 2,2'-bipyridyl followed by a weakly acidic hydrolysis was effective and the substrates having acid sensitive functional groups can be tolerated under the stated conditions. The selective deprotection between methylene acetal and benzopheno...

Fabricating an esthetically pleasing removable partial denture while avoiding the unsightly display associated with conventional clasp assemblies presented a challenge to dentists. Among other techniques, this could be done using acetal resin clasps as simple and effective means of improving removable partial denture esthetics.1 Patients often cite lack of retention and poor esthetics as reason...