Design, synthesis, and biological evaluation of tricyclic nucleosides (dimensional probes) as analogues of certain antiviral polyhalogenated benzimidazole ribonucleosides.

The polyhalogenated benzimidazole nucleosides 2,5, 6-trichloro-1-(beta-D-ribofuranosyl)benzimidazole (TCRB) and the 2-bromo analogue (BDCRB) were synthesized in our laboratory and established as potent and selective inhibitors of human cytomegalovirus (HCMV) with a novel mode of action. In an effort to study the behavior of the key substructure in a dimensionally extended manner and probe the spatial limitation of the target enzyme(s), a series of 2-substituted 6, 7-dichloro-1-(beta-D-ribofuranosyl)naphtho¿2,3-dimidazoles and the N1- and N3-ribonucleosides of 2-substituted 6,7-dichloroimidazo¿4, 5-bquinolines were prepared. The nucleosides 6, 7-dichloro-1-(beta-D-ribofuranosyl)imidazo¿4,5-bquinolin-2-one and 6,7-dichloro-3-(beta-D-ribofuranosyl)imidazo¿4,5-bquinolin-2-one were selected and used as the key synthetic intermediates in the imidazo¿4,5-bquinoline series. Evaluation of the compounds for activity against HCMV and herpes simplex virus type 1 revealed that the trichloro analogues of TCRB (2a, 3a) were nearly as active against HCMV as TCRB but were more cytotoxic. The results suggest that extending the heterocycle of TCRB affected the affinity for the HCMV target only slightly but increased the affinity for cellular enzymes.

The rational design of potential chemotherapeutic agents: synthesis of bryostatin analogues.

The bryostatins are a unique family of cancer chemotherapeutic candidates isolated from marine bryozoa. While their molecular mode of action is not known, these macrolactones exhibit high affinities for protein kinase C (PKC) isozymes, compete for the phorbol ester binding site on PKC, and stimulate kinase activity in vitro and in vivo. Unlike the phorbol esters, they do not act as tumor promoters. Despite promising biological properties, the supply of these compounds is limited by the difficulty of their isolation from natural sources and their synthetic complexity. A new class of bryostatin analogues which retain the putative recognition domain of the bryostatins but are simplified through deletions and modifications in the C1-C14 spacer domain have been designed using computer models. A convergent synthesis has been realized for the production, in gram quantities, of these recognition and spacer domains whose coupling allows for the generation of a range of analogues. The final closure process involves a novel macrotransacetalization reaction which proceeds with complete stereoselectivity. The solution structures of two synthetic analogues were determined by NMR spectroscopy and found to be very similar to the previously reported structures of bryostatins 1 and 10. In addition, these structures appear to indicate that the stereochemistry of the C3 hydroxyl group plays a significant role in the conformation of the macrolactone. All analogues bound strongly to a mixture of PKC isozymes, and several exhibited significant levels of in vitro growth inhibitory activity against human cancer cell lines. Taken together, this work provides important steps toward the development and understanding of simplified, synthetically accessible analogues of the bryostatins as potential chemotherapeutic agents.

Selective binding of bryostatin analogues to the cysteine rich domains of protein kinase C isozymes.

Designed bryostatin analogues are assayed for binding affinity to individual cysteine rich domains of several protein kinase C (PKC) isozymes. These analogues exhibit significant selectivity for the PKCdelta-C1B peptide in terms of absolute affinity and the PKCdelta-C1A peptide in terms of relative affinity when compared to phorbol-12,13-dibutyrate.

The design, computer modeling, solution structure, and biological evaluation of synthetic analogs of bryostatin 1.

The bryostatins are a unique family of emerging cancer chemotherapeutic candidates isolated from marine bryozoa. Although the biochemical basis for their therapeutic activity is not known, these macrolactones exhibit high affinities for protein kinase C (PKC) isozymes, compete for the phorbol ester binding site on PKC, and stimulate kinase activity in vitro and in vivo. Unlike the phorbol esters, they are not first-stage tumor promoters. The design, computer modeling, NMR solution structure, PKC binding, and functional assays of a unique class of synthetic bryostatin analogs are described. These analogs (7b, 7c, and 8) retain the putative recognition domain of the bryostatins but are simplified through deletions and modifications in the C4-C14 spacer domain. Computer modeling of an analog prototype (7a) indicates that it exists preferentially in two distinct conformational classes, one in close agreement with the crystal structure of bryostatin 1. The solution structure of synthetic analog 7c was determined by NMR spectroscopy and found to be very similar to the previously reported structures of bryostatins 1 and 10. Analogs 7b, 7c, and 8 bound strongly to PKC isozymes with Ki = 297, 3.4, and 8.3 nM, respectively. Control 7d, like the corresponding bryostatin derivative, exhibited weak PKC affinity, as did the derivative, 9, lacking the spacer domain. Like bryostatin, acetal 7c exhibited significant levels of in vitro growth inhibitory activity (1.8-170 ng/ml) against several human cancer cell lines, providing an important step toward the development of simplified, synthetically accessible analogs of the bryostatins.

Drug-exposed infants at home: strategies and supports.

This longitudinal, descriptive study gathered information on drug-exposed infants at home and identified effective public health nurse interventions for them and their caregivers. These infants exhibit symptoms that may well interfere with their ability to give clear cues as part of the infant-caregiver interactive system. This may amplify or perpetuate the effects of the drugs and low birth weight. Fifteen infants with a positive toxicology screen were compared to controls at birth and followed for up to 12 months of age through home visits by a public health nurse practitioner. The drug-exposed infants were significantly smaller at birth, and their most common initial problems were the need for nonnutritive sucking, excessive extensor tone, infections, and irritability. The mean weight, length, and head circumference went from the 10th to the 25th percentile at birth to the 25th to 50th percentile at 12 months. The support system and organization of the home predicted the family's ability to sustain caregiving for these infants. Effective strategies to care for these infants included recognizing states and cues, swaddling, use of pacifier, waking to eat, and smaller feedings. The role of the public health nurse was crucial for conducting early assessment, implementing strategies, and facilitating a therapeutic relationship.