The DPD is a very unstable compound that reacts with water and
cyclizes to form several furanones, one of which is thought to be the precursor of AI-2 (SCHAUDER et al., 2001).
1,3-Hydrogen shift occurs to give an isomeric enamine (B) that
cyclizes to give the seven- membered ring product.
Indeed, 2-(tosyloxymethyl) aziridines 228a,b undergo initial nucleophilic displacement of the tosyloxy group by means of o-aminothiophenol towards intermediate aziridines 233, which
cyclizes spontaneously to afford 4-substituted 3-aminobenzothiazepines 231 (pathway a).
Upon formation, DPD spontaneously
cyclizes to form at least two different interspecies communication molecules described as AI-2 [5].
Compound 1 boils with a mixture of acetic acid/acetic anhydride gives the intermediate compound 2 which
cyclizes to 5-acetyl-2-amino-4-phenylthiophene-3-carbonitrile 3.
The [alpha]-keto acid spontaneously
cyclizes to form enamine/imine tautomers; but at the naturally acidic pH of ink, the [alpha]-keto acid dominates.
In contrast, more than 99% of aldosterone
cyclizes, with the alde- hyde group at carbon 18 reacting with the hydroxyl at carbon 11, forming a stable 11,18 hemiacetal.
In the absence of Cu, the bisozaxoline-modified bisthiophene
cyclizes without any control of stereochemistry, giving equal mixtures of the (S,S)-(R,R) and (S,S)-(S,S) diastereomers.
For example, glutaminyl cyclase (QC)
cyclizes N-terminal glutamine to pyro-glutamine to produce a biologically active peptide.
Glutaminyl cyclase
cyclizes N-terminal glutamine to pyroglutamic acid in such peptides as TRH.
TABLE I ELECTRICAL PROPERTIES OF TYPICAL MATRIX RESINS|1~ Matrix Resins Dielectric Constant Loss Tangent Polyester 2.7 to 3.2 0.005 to 0.02 Epoxy 3.0 to 3.4 0.01 to 0.03 Cyanate ester 2.7 to 3.2 0.004 to 0.01 Polymide 2.7 to 3.2 0.005 to 0.007 Polyetherketone 3.1 0.004 Polybutadiene|4~ 2.2 0.0005 Epoxy-Anhydride-PBD 2.502 0.007 Since this system cures with a peroxide at 150|degrees~C, and thermally
cyclizes at 240|degrees~C, plus or minus a few degrees, it has some built-in heat resistance.