Gastroenterologists and choosing the right bisphosphonate

Ru(II)-Catalyzed Enantioselective Transfer Hydrogenation of α-Ketophosphonates: Straightforward Access to Valuable Chiral α-Hydroxy Phosphonates

Asymmetric transfer hydrogenation (ATH) is arguably one of the most powerful tools for the synthesis of chiral compounds. Despite tremendous advances in this field, the reduction of α-ketophosphonates remains largely unexplored. Herein, we report an efficient Ru-catalyzed ATH on a broad range of α-ketophosphonates. Compared with existing methods, our approach offers as advantages mild conditions, operational simplicity, limited waste generation, broad substrate scope (26 examples), good to excellent yields (75-93%), and excellent levels of stereoinduction (from 90% to >99% ee).

Enantioselective biocatalytic resolution for the synthesis of enantiopure α-hydroxyphosphonates using Candida antarctica lipase B

A versatile and efficient method to produce enantiopure α-hydroxyphosphonates and their acyl transfer products using CALB under mild conditions.

Organocatalytic decarboxylative aldol reaction of β-ketoacids with α-ketophosphonates en route to the enantioselective synthesis of tertiary α-hydroxyphosphonates

γ-Aroyl tertiary α-hydroxyphosphonates with a chiral quaternary centre were synthesized via a facile organocatalyzed decarboxylative aldol reaction between β-ketoacids and α-ketophosphonates.

RAFT copolymerization of a phosphorus-containing monomer with α-hydroxy phosphonate and methyl methacrylate

RAFT copolymerization of a phosphorus-containing monomer with α-hydroxy phosphonate PHMA and MMA was successfully conducted and the resultant well-defined copolymer material shows good superior flame-retardant properties and hydrophilicity.

2,6-Dimethylphenol derived H-phosphonate and α-hydroxyphosphonate: facile synthesis, crystal chemistry, supramolecular association and metal complexation

A H-phosphonate and an α-hydroxyarylphosphonate with active P–H and P–OH groups have been synthesized from 2,6-dimethylphenol and their aggregation behavior has been investigated.

Addition of optically pure H-phosphinate to ketones: selectivity, stereochemistry and mechanism

A stability-controlled diastereoselective addition of a chiral P–H species to ketones afforded P,C-stereogenic α-hydroxyphosphinates in excellent yields and dr.

Organocatalytic High Enantioselective Synthesis of β-Formyl-α-hydroxyphosphonates

The cross aldol reaction between enolizable aldehydes and α-ketophosphonates was achieved for the first time by using 9-amino-9-deoxy-epi-quinine as the catalyst. β-Formyl-α-hydroxyphosphonates were obtained in high to excellent enantioselectivities. The reaction works especially well with acetaldehyde, which is a tough substrate for organocatalyzed cross aldol reactions. The products were demonstrated to have anticancer activities.

Developing novel organocatalyzed aldol reactions for the enantioselective synthesis of biologically active molecules

Aldol reaction is one of the most important methods for the formation of carbon-carbon bonds. Because of its significance and usefulness, asymmetric versions of this reaction have been realized with different approaches in the past. Over the last decade, the area of organocatalysis has made significant progresses. As one of most studied reactions in organocatalyses, organocatalyzed aldol reaction has emerged as a powerful tool for the synthesis of a large number of useful products in optically enriched forms. In this review, we summarize our efforts on the development of novel organocatalyzed aldol reactions for the enantioselective synthesis of biological active molecules. Literatures closely related to our studies are also covered.

Organocatalytic asymmetric synthesis of organophosphorus compounds

240 Years have passed since the discovery of elemental phosphorus. During that time organophosphorus chemistry has emerged as an interesting and exciting field of research. Recently organophosphorus chemistry has been raised to a new level. Organophosphorus compounds have found applications in asymmetric organocatalysis for the synthesis of optically active compounds of synthetic or biological importance. The aim of this review article is to present recent contributions to this developing field of chemistry and to point out synthetic advantages of methodologies developed so far.

Chiral biphenylamide derivative: an efficient organocatalyst for the enantioselective synthesis of alpha-hydroxy phosphonates

The aldol reactions of alpha-keto phosphonates and aldehydes were facilitated by an axially chiral biphenylprolinamide under mild conditions, affording the synthetically and pharmaceutically useful products in high yields and excellent enantioselectivities.

[Comparison of clinical characteristics and outcomes between geriatric and non-geriatric patients in peptic ulcer bleeding]

BACKGROUND/AIMS

In geriatric patients with peptic ulcer, the use of NSAID and prevalence of chronic illness have been increased, but the Helicobacter pylori (H. pylori) infected portion decreased. The aim of this study was to evaluate the clinical characteristics and outcomes of geriatric patients (aged 65 or older) with peptic ulcer bleeding and compare with non-geriatric patients (less than 65 years old).

METHODS

We conducted a retrospective study of 88 patients with peptic ulcer bleeding treated with therapeutic endoscopy from January 2006 to December 2006. We compared the clinical characteristics and outcomes of geriatric patients (n=34, 38.6%) with those of non-geriatric patients (n=54, 61.4%).

RESULTS

Hypertension (52.9% vs. 24.1%), cardiovascular disease (35.3% vs. 13.0%), and chronic obstructive pulmonary disease (20.6% vs. 3.7%) were more prevalent in the geriatric group, compared with the non-geriatric group (p<0.05). The geriatric group had taken more ulcerogenic drugs than the non-geriatric group (64.7% vs. 33.3%, p<0.05); aspirin plus clopidogrel (23.6% vs. 13.0%) and aspirin (20.6% vs. 11.0%). Sixteen (21.1%) of the 76 cases had H. pylori-negative ulcer. Between the two groups, there was no difference in the prevalence of H. pylori-negative ulcer (25.9% vs. 18.4%, p>0.05). The amount of transfusion length of ICU stay, rebleeding rate, operation rate and mortality were not different between the two groups. The length of hospital stay in the geriatric patients was significantly longer than the non-geriatric group (12.3+/-10.6 vs. 7.2+/-5.9 days, p<0.05). In multiple regression analysis, old age was a significant risk factor for longer hospital stay (p<0.05).

CONCLUSIONS

The geriatric patients with bleeding peptic ulcer had longer hospital stay than the non-geriatric patients in our study. The important emerging etiologies such as ulcerogenic drug and associated chronic illness should be checked and treated in these patients.

Preventive effect of risedronate on bone loss in men receiving androgen-deprivation therapy for prostate cancer

AIM

Androgen-deprivation therapy for prostate cancer decreases bone mineral density and increases the risk of fracture. The effect of risedronate, a potent third-generation oral bisphosphonate, on bone loss during androgen deprivation therapy was investigated.

METHODS

Sixty-one prostate cancer patients with a mean age (+/- SD) of 79 +/- 6 years who had received androgen deprivation therapy for 42 +/- 29 months were enrolled, and were treated with 2.5 mg of risedronate daily for six months. Bone mineral density was measured at the femoral neck, lumbar spine, and ultradistal radius by dual energy X-ray absorptiometry. The percent change of bone mineral density after treatment with risedronate was calculated as the primary efficacy variable. Urinary N-telopeptide of type I collagen was measured as a bone resorption marker.

RESULTS

Bone mineral density remained stable in the femoral neck and radius during risedronate therapy. In contrast, the bone mineral density of the lumbar spine showed a significant increase from 1069 +/- 488 mg/cm(2)-1112 +/- 497 mg/cm(2) (P < 0.001), representing a gain of 4.9 +/- 8.9%. Urinary N-telopeptide of type I collagen decreased significantly (P < 0.001) after three months of risedronate treatment.

CONCLUSIONS

Risedronate could prevent and reverse bone loss in men receiving androgen deprivation therapy for prostate cancer by inhibiting bone resorption.

Organocatalytic highly enantioselective synthesis of secondary alpha-hydroxyphosphonates

[reaction: see text] The first organocatalytic cross aldol reaction of ketones and diethyl formylphosphonate hydrate has been realized by using readily available l-prolinamide as the catalyst. Secondary alpha-hydroxyphosphonates have been synthesized in high enantioselective (up to >99% ee) and good diastereoselectivity.

Organocatalytic enantioselective synthesis of alpha-hydroxy phosphonates

Tertiary alpha-hydroxy phosphonates have been synthesized in good yields and high enantiomeric purity (up to 99% ee) through a novel l-proline-catalyzed cross aldol reaction of alpha-keto phosphonates and ketones.

Absorption of the oral bisphosphonate alendronate in osteoporotic patients with Crohn's disease

The absorption of bisphosphonates from the gut is poor. The question arises whether the absorption of alendronate, and thus its bioavailability, is further altered by the local inflammatory process in patients with Crohn's disease, thereby potentially affecting clinical outcome when used in the treatment of osteoporosis. To address this question, urinary excretion of alendronate was evaluated 3 months and 6 months after start of treatment with oral alendronate at a dose of 10 mg/day in 19 osteoporotic patients with stable Crohn's disease, 12 of whom had an intestinal resection. Biochemical parameters of bone turnover and BMD were also measured at start and at 6 months. Thirteen patients had been previously treated with glucocorticoids and five were currently using them. The average 24-h urinary excretion of alendronate was 0.5-0.6% of the dose administered, a figure comparable to that reported for osteoporotic patients without gut pathology. There was a significant decrease from baseline in urine N-telopeptides of collagen cross-links (NTx)/creatinine (60%) associated with an increase in lumbar spine BMD of already 2% after 6 months of treatment. Our data suggest that in patients with Crohn's disease, alendronate is adequately absorbed from the intestine and retained in the skeleton. This adequacy is confirmed by appropriate suppression of bone resorption and increase in lumbar spine BMD. These data hold significant implications for the clinical management of patients with Crohn's disease and osteoporosis.

DT56a (Femarelle) stimulates bone formation in female rats

OBJECTIVE

DT56a is a natural compound for the treatment of menopausal symptoms and osteoporosis. The aim of this study was to examine the effects of long term treatment (two months) with DT56a on the skeletal tissues of intact and ovariectomised (OVX) adult rats.

DESIGN

Thirty rats were divided into two groups, in one of which the rats were ovariectomised. The rats in each group were then treated for two months with DT56a, oestrogen or vehicle.

SETTING

University and hospital laboratories.

POPULATION

Thirty rats.

METHODS

Histomorphometric measurements of trabecular bone volume (expressed as a percentage of total bone volume), trabecular and cortical thickness and growth plate width were recorded by a computerised system. In addition, creatine kinase (CK)-specific activity, as marker of oestrogen receptor activation, was measured in skeletal tissues and in the uterus.

MAIN OUTCOME MEASURES

The changes in the histomorphometric measurements.

RESULTS

OVX rats developed noticeable signs of osteoporosis, namely, significant decrease in trabecular bone volume and in trabecular and cortical thickness. DT56a, like oestrogen, restored the bone structure measurements of all tested parameters in the OVX rats to the values obtained in the intact rats. In skeletal tissues, CK activity was elevated in both treatment groups. However, in the uterus DT56a did not activate oestrogen receptors while oestrogen did elevate CK activity.

CONCLUSIONS

DT56a was as effective as oestrogen in reversing the bone changes caused by OVX in rats.

Alendronate treatment for infants with osteogenesis imperfecta: demonstration of efficacy in a mouse model

Recent non-placebo-controlled studies of the bisphosphonate pamidronate have shown it to be effective in reducing fractures and improving bone density in infants and children with osteogenesis imperfecta (OI). To evaluate the effects of bisphosphonate treatment in a controlled study, the oim/oim mouse model of OI was studied. Nursing infant mouse pups (approximately 2 wk old) with moderate to severe OI (oim/oim mouse) and age- and background-matched control mice (+/+) were treated either with the third-generation bisphosphonate alendronate (ALN), or with saline. Fracture risk, bone quality, and growth were evaluated over a 12-wk treatment period. ALN at a dose of 0.03 mg/kg/d or saline was administered via s.c. injection to infant oim/oim and wild-type (+/+) mice from 2 to 14 wk of age (n = 20 per subgroup). The average number of fractures sustained by the ALN-treated oim/oim mice was reduced significantly compared with the untreated oim/oim mice (0.7 +/- 0.7 fractures/mouse versus 2.0 +/- 0.2 fractures/mouse). Bone density increased significantly in the femur and the spine with treatment (2.0 +/- 0.5 versus 1.2 +/- 0.5 in femur and 2.1 +/- 0.5 versus1.6 +/- 0.5 in spine). Histologic evaluation revealed the percentage of metaphyseal tibial bone increased significantly with treatment in both +/+ and oim/oim mice. Mechanical testing revealed an increase in structural stiffness for both treated +/+ and oim/oim mice compared with untreated animals. None of the material properties examined were significantly altered with treatment, nor was spinal curvature affected. Weight gain and long bone growth were comparable in the treated and untreated oim/oim mice. In wild-type mice, femur lengths were significantly shorter in the treated mice compared with untreated counterparts. This animal study demonstrates that treatment of OI in mice as early as 2 wk of age with ALN appears to be effective in reducing fractures and increasing bone properties. Based on the data from this study, ALN therapy in infants with OI should prove to be effective.

Oral bisphosphonates and upper gastrointestinal tract problems: what is the evidence?

OBJECTIVE

To review and evaluate the evidence regarding possible associations of bisphosphonate use with upper gastrointestinal (GI) tract adverse events (AEs).

METHODS

We reviewed and summarized published information and abstracts regarding upper GI tract safety and tolerability of bisphosphonates, including laboratory and animal studies, epidemiological (observational) studies, endoscopy studies, and randomized controlled trials (RCTs). The evidence was summarized by using the principles of evidence-based medicine, giving the greatest credence to high-quality RCTs.

RESULTS

Clinical reports of esophagitis associated with bisphosphonate use appear to have declined in frequency once the importance of proper administration was explained to physicians after early reports of complications. Conflicting results have been reported in endoscopy studies; some reported no significant increase in upper GI tract lesions, whereas others reported a higher incidence of gastric (but not esophageal) lesions among patients taking oral bisphosphonates. Endoscopy studies that reported differences were of short duration (2 weeks) and were not of double-blind design. Results from large RCTs involving thousands of participants detected no increase in upper GI tract AEs among individuals treated with bisphosphonates. Other studies of patients who discontinued taking bisphosphonates and were randomized to blinded re-treatment with either a bisphosphonate or placebo show that most patients (>85%) were able to continue treatment, with no difference in AEs between the bisphosphonate and placebo groups.

CONCLUSIONS

The highest level of evidence, RCTs, suggests little or no increase in risk of upper GI tract problems if bisphosphonates are administered properly. Upper GI tract symptoms are common among patients with osteoporosis. The evidence suggests that many upper GI tract AEs reported during therapy with bisphosphonates may reflect a high background incidence of upper GI tract complaints and an increased sensitivity to detection rather than a causal relationship to therapy.

Gastrointestinal Adverse Effects of Bisphosphonates

The bisphosphonate class of drugs are now utilized extensively in the treatment of patients with osteoporosis and Paget's disease. Gastrointestinal (GI) adverse effects, especially those associated with esophageal injury, have been of increasing concern to clinicians. Studies in humans and animals have shown that the mucosal erosion and ulceration seen with bisphosphonates is a result of direct contact with these agents. Numerous endoscopic studies in healthy volunteers and postmenopausal women have also demonstrated the potential of bisphosphonates to cause stomach and duodenal ulcers. However, serious GI adverse events have not been noted in several large efficacy trials. Esophageal injury has for the most part been avoided by appropriate administration instructions, and gastroduodenal injury appears to be an acute phenomenon not associated with significant complications, except in certain high-risk situations, for example in the presence of existing distal esophageal disease or motility disorders, or with concurrent use of nonsteroidal anti-inflammatory drugs or anticoagulants. From the standpoint of GI safety, the bisphosphonates are well tolerated and not associated with serious adverse events.

Review of risedronate in the treatment of osteoporosis

Risedronate (Actonel, Procter & Gamble and Aventis) is a novel, orally administered pyridinyl bisphosphonate. Preclinical studies have shown that risedronate is a potent inhibitor of osteoclasts. Risedronate inhibited bone resorption and increased bone density in the spine and hip. Prospective, randomised, placebo-controlled trials (RCTs) in patients with postmenopausal osteoporosis (PMO) have demonstrated that risedronate decreased the risk of vertebral fractures by up to 49% and of non-vertebral fractures by up to 39% over 3 years in postmenopausal women with one or more prevalent vertebral fractures. This reduction of the risk for vertebral fractures was significant from the first year of treatment (risk reduction up to 65%). Risedronate was the first bisphosphonate to be studied in a large RCT with prevention of hip fracture as the primary end point. In this study, risedronate reduced the risk of hip fracture by 40% in elderly women with low hip bone density and one clinical risk factor for hip fracture and by 60% in women with low bone density and a prevalent vertebral fracture at baseline. Risedronate was also effective in the prevention and treatment of bone loss in glucocorticoid-induced osteoporosis (GIO), with a positive effect on vertebral fractures within the first year. Risedronate was well-tolerated with a safety profile comparable to placebo in all clinical studies. Patients with a previous or current history of upper GI illness or who were taking NSAIDs or aspirin were not excluded from these studies. Importantly, the upper GI safety profile of risedronate was shown to be similar to that of placebo in endoscopic studies. There was no evidence of acute-phase reactions or primary mineralisation defects. The most appropriate dose of risedronate was 5 mg/day.