David Linder

Glucose-6-Phosphate Dehydrogenase Mosaicism: Utilization as a Cell Marker in the Study of Leiomyomas

The sex-linked electrophoretic variants A and B of glucose-6-phosphate dehydrogenase were studied in 86 samples of myometrium and 27 leiomyomas from five heterozygous women. All but one sample of myometrium had both A and B bands in equal or nearly equal amounts. In contrast to this, all of the leiomyomas had either an A band or a B band. Both A and B tumors were found in all uteri. These findings are consistent with the hypothesis that these tumors arose from single cells.

Parthenogenic Origin of Benign Ovarian Teratomas

To determine the origin of benign cystic teratomas of the ovary, chromosome-banding studies were done on normal tissues and teratomas from five patients. The normal tissues were heterozygous (+/-) for 17 chromosome polymorphisms at or near the centromere, whereas the teratomas were uniformly homozygous (+/+ or -/-). These findings and those employing electrophoretic variants indicate that ovarian teratomas are parthenogenic tumors that arise from a single germ cell after the first meiotic division.

Self-assembled hexanuclear arene ruthenium metallo-prisms with unexpected double helical chirality

Self-assembly of 2,4,6-tripyridyl-1,3,5-triazine (tpt) subunits with arene ruthenium building blocks and oxalato bridges affords cationic triangular metallo-prisms of the type [Ru6(arene)6(tpt)2(C2O4)3]6+ (arene = C6Me6 and p-Pr(i)C6H4Me); the unexpected double helical chirality of the metallo-prisms observed in the solid state persists in solution giving rise to two different stereodynamic processes as demonstrated by NMR enantiodifferentiation experiments.

Origin of extragonadal teratomas and endodermal sinus tumours

TERATOMAS are usually differentiated tumours, containing tissues derived from ectoderm, endoderm and mesoderm, and may arise in the gonads or elsewhere. Benign ovarian teratomas are parthenogenetic tumours derived from a single germ cell after the first division of meiosis, as studies of chromosome markers and enzyme variants have shown1,2. We have now found that extragonadal teratomas develop in a different manner. We have examined single gene products and chromosomes in extragonadal teratomas and report here our results. We include data on endodermal sinus tumours because of their similarity to teratomas3,4.

Enantioselective and Regioselective Ruthenium‐Catalyzed Decarboxylative Etherification of Allyl Aryl Carbonates

Simple ligand, catalyst and conditions: The combination of readily-prepared pyridylmonooxazolines (pymox) ligands and [CpRu(CH3CN)3][PF6] affords a regio- and enantioselective decarboxylative etherification of allyl aryl carbonates. This is the first successful example of this type of etherification reaction.

Chiral or not chiral? A case study of the hexanuclear metalloprisms [Cp(6)M(6)(micro(3)-tpt-kappaN)(2)(micro-C2O4-kappaO)(3)]6+ (M = Rh, Ir, tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine).

Cationic hexarhodium and hexairidium complexes with a trigonal prismatic architecture have been synthesised in good yield by self-assembly of the dinuclear oxalato-bridged complexes [Cp(2)M(2)(micro-C(2)O(4)-kappaO)Cl(2)] (M = Rh; 1: Ir; 2) with 2,4,6-tri(pyridine-4-yl)-1,3,5-triazine (tpt) in the presence of AgO(3)SCF(3). The trigonal prismatic cations [Cp(6)Rh(6)(micro(3)-tpt-kappaN)(2)(micro-C(2)O(4)-kappaO)(3)](6+) (3) and [Cp(6)Ir(6)(micro(3)-tpt-kappaN)(2)(micro-C(2)O(4)-kappaO)(3)](6+) (4) have been isolated as their triflate salts. The single-crystal X-ray structure analysis of [3][O(3)SCF(3)](6) shows two enantiomers in the racemic crystal (space group C2/c), the chirality being due to a twist of the two tpt units. By contrast, the single-crystal X-ray structure analysis of [4][O(3)SCF(3)](6) shows a perfectly eclipsed conformation of the tpt units, so that is not chiral in the crystal state (space group Fd3[combining macron]c). However, in solution, enantiodifferentiation in the presence of the chiral anion Delta-BINPHAT is observed by (1)H NMR spectrometry not only in the case of 3, but also in the case of 4. This suggests that the iridium derivative 4, which is not chiral in the solid state, adopts chiral conformations in solution.

Estimating distances from the centromere by means of benign ovarian teratomas in man.

Under the assumption that benign ovarian teratomas in man arise parthenogenically from a germ cell by suppression of the second meiotic division, the distance of a gene from its centromere can be estimated from the observed proportion of heterozygous teratomas collected from heterozygous hosts. The frequency of heterozygous teratomas of heterozygous hosts is equivalent to the frequency of second division segregation at the gene locus which has been used for centromere-related mapping in fungal genetics for more than 40 years. Mapping functions useful for teratoma-based mapping in man are presented.

Self-adaptable catalysts: substrate-dependent ligand configuration.

Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5-dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C(s) conformation in both eta3-1,3-diphenylpropenyl and eta3-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C2 and pseudo-C(s) symmetric ligands.

Enantio- and regioselective CpRu-catalyzed Carroll rearrangement*

The addition of unstabilized carbonyl nucleophiles to allyl-metal fragments still represents a challenge for generating stereoselectively tertiary (and quaternary) stereogenic centers. In this context, the decarboxylative Carroll rearrangement of secondary and tertiary allyl β-ketoesters is particularly interesting since chiral γ,δ-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, in the presence of selected enantiopure diimine ligands, catalyze this transformation and afford complete conversions and decent level of enantiomeric excess. Zwitterionic adducts of a hexacoordinated phosphorus anion and CpRu moieties were also associated and shown to generate air-, moisture-, and microwave-stable catalysts that can be readily purified and recycled. Carroll rearrangements of allylic β-ketoesters performed with these zwitterionic species occur with better regio- and enantioselectivity.