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Diacylglycerol acyltransferase (DGAT) catalyzes the final step in triglyceride (TG) synthesis. There are two isoforms, DGAT1 and DGAT2, with distinct protein sequences and potentially different physiological functions. To date, the ability to determine clear functional differences between DGAT1 and DGAT2, especially with respect to hepatic TG synthesis, has been elusive. To dissect the roles of these two key enzymes, we pretreated HepG2 hepatoma cells with (13)C(3)-D(5)-glycerol or (13)C(18)-oleic acid, and profiled the major isotope-labeled TG species by liquid chromatography tandem mass spectrometry. Selective DGAT1 and DGAT2 inhibitors demonstrated that (13)C(3)-D(5)-glycerol-incorporated TG synthesis was mediated by DGAT2, not DGAT1. Conversely, (13)C(18)-oleoyl-incorporated TG synthesis was predominantly mediated by DGAT1. To trace hepatic TG synthesis and VLDL triglyceride (VLDL-TG) secretion in vivo, we administered D(5)-glycerol to mice and measured plasma levels of D(5)-glycerol-incorporated TG. Treatment with an antisense oligonucleotide (ASO) to DGAT2 led to a significant reduction in D(5)-glycerol incorporation into VLDL-TG. In contrast, the DGAT2 ASO had no effect on the incorporation of exogenously administered (13)C(18)-oleic acid into VLDL-TG. Thus, our results indicate that DGAT1 and DGAT2 mediate distinct hepatic functions: DGAT2 is primarily responsible for incorporating endogenously synthesized FAs into TG, whereas DGAT1 plays a greater role in esterifying exogenous FAs to glycerol.

The syntheses of the Fmoc-protected Peptide Nucleic Acid (PNA) monomer pentafluorophenyl esters of adenine (26), cytosine (23), guanine (29) and thymine (20), and their oligomerization are described. The Fmoc PNA backbone 1 is prepared as a stable hydrochloride salt. The base acetic acids of adenine (4) and cytosine (3) were prepared by Cbz protection of the exocyclic amino groups followed by alkylation with t-butylbromoacetate and subsequent acid hydrolysis of the t-butyl ester. Allylation of 6-chloro-2-aminopurine followed by acid hydrolysis, Cbz protection with N-(benzyloxycarbonyl)imidazole, ozonolytic cleavage, and oxidation afforded the Cbz-protected guanine acetic acid (5). The base acetic acids (2, 3, 4 and 5) were coupled to the backbone (1) with either EDC (2 and 3) or BOP reagent (4 and 5). Acid hydrolysis of the resulting t-butyl esters and transesterification afforded the corresponding pentafluorophenyl esters (20, 23, 26 and 29). Oligomerization is conducted on a 0.05 mmol scale with a mere 2 fold excess of monomer in each coupling cycle. The N-terminal Fmoc group is retained on the final oligomer, following HF cleavage and deprotection, providing a convenient lipophilic handle for HPLC purification.

Several cases of significant enhancement in the diastereoselectivity of acyclic Claisen rearrangement of cyclohexenyl allyl ethers governed principally by remote asymmetric center(s) have been observed when Lewis acid catalysts are employed rather than the usual thermal rearrangement conditions.

Peptide nucleic acids (PNA) are oligodeoxynucleotide (ODN) analogs in which the sugar phosphate backbone of the ODN has been replaced by one derived from units of N-ethylaminoglycine. PNAs recognize DNA and RNA in a sequence specific manner and form complexes that can be characterized by biophysical methods. The binding motif is context dependent; homopyrimidine PNAs combine with complementary polypurine targets to form stoichiometric 2:1 complexes, whereas PNAs containing both purine and pyrimidine bases afford a 1:1 heteroduplex with mis-match sensitivity comparable to that found in dsDNA. These complexes mediate the antigene and antisense effects of PNAs via the steric blockade of enzyme complexes responsible for DNA transcription, cDNA synthesis, and RNA translation. PNAs, like ODNs, are taken up by cells via endocytosis leading to their entrapment within intracytoplasmic vesicles. Under circumstances where agent delivery is solved by cell microinjection, PNAs can effect selective inhibition of endogenous and exogenous genes. The impact of biophysical parameters on the biological assessment of PNAs as antisense inhibitors of gene expression is presented and discussed. © 1995 Wiley-Liss, Inc.

N-Substituted 2-azanorbornenes undergo a 9-borabicyclo [3.3.1]nonane induced fragmentation in tetrahydrofuran giving rise to cyclopentenylmethyl amines (cf 3 and 5).

We have identified a novel class of 6-thiazolylquinazolines as potent and selective inhibitors of both ErbB-2 and EGFR tyrosine kinase activity, with IC(50) values in the nanomolar range. These compounds inhibited the growth of both EGFR (HN5) and ErbB-2 (BT474) over-expressing human tumor cell lines in vitro. Using xenograft models of the same cell lines, we found that the compounds given orally inhibited in vivo tumor growth significantly compared with control animals.

The chiral 2-oxocyclopentanecarboxylates (II) are prepared by Rh-catalyzed ring closure of the α-diazo-β-ketoesters (I).

Etude de la reduction d'esters de [naphtyl-1]-3 bornanaryle-2 de β-oxacides en hydroxyacides diastereoisomeres par Zn(BH 4 ) 2 /ZnCl 2 ou par le DIBAL/BHT; transformation d'un des hydroxyesters obtenus, l'hydroxy-3 myristate de [naphtyl-1]-3 bornanyle-2 en (−)-undecyl-6 perhydro pyranonne-2

The chiral 2-oxocyclopentanecarboxylates (II) are prepared by Rh-catalyzed ring closure of the α-diazo-β-ketoesters (I).