Asymmetric total synthesis of 1-deoxy-7,8-di-epi-castanospermine

An efficient, stereocontrolled synthesis of (6S,7S,8S,8aR)-6,7,8-trihydroxyindolizidine (alias 1-deoxy-7,8-di-epi-castanospermine) (14) has been developed, which exploits an asymmetric vinylogous Mukaiyama aldol reaction (VMAR) between N-(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyloxy)pyrrole (1) and 2,3-O-isopropylidene-D-glyceraldehyde (2) to construct the initial pyrrolidine building block 3, and an ene-ene ring closing metathesis reaction (RCM) (9 to 10) to install the indolizidine skeleton. The synthetic sequence was 13 steps, proceeding in 19.5% overall yield. The configurational and conformational structure of 14 was ascertained unambiguously and confronted to previously published assignments of rac-14 and ent-14.

Incidence rates of surgically treated idiopathic carpal tunnel syndrome in blue- and white-collar workers and housewives in Tuscany, Italy

OBJECTIVES

Rates of surgically treated carpal tunnel syndrome (CTS) among blue- and white-collar workers and housewives in the general population were compared.

METHODS

Surgically treated cases of idiopathic CTS were investigated among 25-59-year-old residents of Tuscany, Italy, during 1997-2000, based on obligatory discharge records from all Italian public/private hospitals, archived according to residence on Tuscany's regional database. Population data were extracted from the 2001 census.

RESULTS

After excluding repeat admissions, 8801 eligible cases were identified. Age-standardised rates (per 100 000 person-years) of surgical CTS were: "blue-collar women", 367.8; "white-collar women", 88.1; "housewives", 334.5; "blue-collar men", 73.5; and "white-collar men", 15.3. Compared with reference categories (same-sex white-collar workers): female blue-collar workers experienced a 4.2-fold higher standardised rate; housewives, a 3.8-fold excess; and male blue-collar workers, a 4.8-fold excess (all p<0.001). Male and female blue-collar workers showed approximately three to sevenfold higher age-specific rates compared to their white-collar counterparts (all p<0.001). Housewives' rates were similar to those of blue-collar female workers up to 40-44 years of age, after which they were significantly lower (p<0.002). At all ages, housewives' rates were much higher (p<0.001) than those of white-collar women.

CONCLUSIONS

Surgically treated CTS was three to seven times more common (depending on age/gender) in blue-collar than in white-collar workers, which is difficult to explain by differences in body weight or other individual factors. Thus, occupational risk factors seem relevant throughout working life. The high rates for full-time housewives suggest that domestic chores should be investigated as a possible risk factor for CTS.

[Effectiveness studies in the Italian literature on occupational health (1990-2006)]

INTRODUCTION

Evidence-based prevention (EBP) is gaining the growing interest of the scientific community in Occupational Health (OH). To highlight the Italian contribution to EBP, a systematic review was performed, on the main OH-journals publishing in Italian language.

METHODS

Studies that have evaluated interventions carried out to improve workers' health were found out from the articles published in the period 1990-2006, by means of hand-searching. The selected articles were classified on occupational health topics as health intervention, study design, risk factor, authors affiliation.

RESULTS

16 publications were selected, which represent less than 0.5% of all papers published on the 8 Italian journals examined. The most frequent study-design is the pre-post intervention evaluation; 2 out of 16 (25%) studies are randomized trial. The interventions are directed mainly to control the effects of noise and biomechanical overload; textile, health-care and energy production are the most frequent industrial settings. We did not found researches aimed to evaluate the effectiveness of interventions performed in the metalware industry or addressed to injuries prevention.

DISCUSSION

The systematic approach of EBP can be applied to most of the occupational health interventions and effectiveness evaluation should represent a challenge for the occupational health field. The results of the hand searching among publication in Italian could raise interesting debate about methodology and outcomes in the scientific community.

Diastereoselective synthesis of 4,5'-bis-proline compounds via reductive dimerization of N-acyloxyiminium ions

A short, practical synthesis of novel, unsymmetrical 4,5'-bis-proline compounds has been achieved, highlighted by the application of an unprecedented samarium diiodide-driven regio- and diastereocontrolled reductive dimerization of N-acyloxyiminium ions generated from readily available 2-methoxy-5-silyloxymethyl-N-Boc pyrrolidines. The title proline dimers proved to be pertinent metal-free catalysts in aldol and Mannich reactions.

Streamlined, Asymmetric Synthesis of 8,4‘-Oxyneolignans

Highly direct, modular syntheses of several natural 8,4'-oxyneolignans [(-)-1, (+)-1, (-)-2, and (-)-3] and some related variants [(-)-26, (+)-26, (+)-27, and (-)-28] are reported. Utilizing (S)- or (R)-methyl lactate as the chiral sources, two complementary syn- or anti-oriented routes were designed, encompassing nine and five steps, which were carried out to deliver the targets in an enantiomerically pure form. The embodiment of the two independent aryl and aryloxy moieties onto the lactate frame was performed according to a diversity-oriented protocol from the common precursors, aldehydes 6 and ent-6 for the syn-oriented routes and mesyl esters 19 and ent-19 for the anti-oriented routes. These syntheses set the stage for the generation of a wide and diverse repertoire of 8,4'-oxyneolignan compounds and the broad biological interrogation of its members.

A one-pot entry to a novel 3-H-benzo[d]pyrazolo[1,5-b]isothiazole ring system

The phosphorus ylide obtained from the reaction between 2-aminobenzo[d]isothiazol-3-one and dimethyl acetylenedicarboxylate in the presence of triphenylphosphine undergoes a smooth intramolecular Wittig-type reaction to produce, in a one-pot reaction, 3-H-benzo[d]pyrazolo[1,5-b]isothiazole-2,3a-dicarboxylic acid dimethyl ester, a novel functionalized heterocyclic compound.

Grafting aminocyclopentane carboxylic acids onto the RGD tripeptide sequence generates low nanomolar alphaVbeta3/alphaVbeta5 integrin dual binders

Eleven gamma-aminocyclopentane carboxylic acid (Acpca) platforms, including four dihydroxy representatives (19-22), three hydroxy analogues (34-36), and four deoxy derivatives (30-33), were prepared in a chiral nonracemic format. These simple units were then grafted onto an Arg-Gly-Asp (RGD) tripeptide framework by a mixed solid phase/solution protocol delivering an ensemble of 11 macrocyclic analogues of type cyclo-[-Arg-Gly-Asp-Acpca-], 1-11. The individual compounds were evaluated for their binding affinity toward the alphaVbeta3 and alphaVbeta5 integrin receptors. The analogue 10 exhibited a very interesting activity profile (IC50/alphaVbeta3= 1.5 nM; IC50/alphaVbeta5= 0.59 nM), comparable to that of reference compounds EMD121974 and ST1646. Closely related congeners 6, 8, and 9 also proved to be excellent dual binders with activity levels in the low nanomolar range. The three-dimensional (3D) NMR solution structures were determined, and docking studies to X-ray crystal structure of the extracellular segment of integrin alphaVbeta3 in complex with the reference compound EMD121974 were performed on selected analogues to elucidate the interplay between structure and function in these systems and to evidence the subtle bases for receptorial recognition. The results prove that the principle of isosteric dipeptide replacement for peptidomimetics design and synthesis can be violated, without detriment to the development of highly effective integrin binders.

New Enantioselective Entry to Cycloheptane Amino Acid Polyols

[reaction: see text] A diversity-oriented protocol has been developed for the assembly of densely hydroxylated cycloheptane amino acids via succession of a vinylogous Mukaiyama aldol reaction (VMAR), a Morita-Baylis-Hillman reaction (MBHR), and an intramolecular pinacol coupling reaction (IPCR). The plan utilizes D- or L-configured glyceraldehyde derivatives as "chiral" surrogates of glyoxal and N-[(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyl)oxy]pyrrole as the synthetic equivalent of the alpha,gamma-dianion of gamma-aminobutanoic acid. The parallel, asymmetric syntheses of four cycloheptane representatives proceed with high diastereocontrol and virtually complete enantioselectivity in ten steps and overall yields of 15-37%.

Enantioselective Total Synthesis of (1R,3S,4R,5R)-1-Amino-4,5-dihydroxycyclopentane-1,3-dicarboxylic Acid. A Full-Aldol Access to Carbaketose Derivatives

The enantioselective synthesis of cyclopentanedicarboxylic amino acid 1, a novel rigid and functionalized L-glutamic acid analogue, has been achieved in 15 linear steps from silyloxypyrrole 3, utilizing L-glyceraldehyde 4 as the source of chirality. The key steps in the synthesis are three sequential aldol-based carbon-carbon bond-forming reactions: two crossed vinylogous aldol additions (2 + 3 --> 8 and 4 + 5 --> 10 + 11) and one intramolecular silylative aldolization (6 --> 7). En passant, the short syntheses of (2S)-2-hydroxymethylglutamic acid (16) and its (2R)-enantiomer ent-16, a potent metabotropic glutamate receptor agonist, have been achieved.

Variable Strategy toward Carbasugars and Relatives. 6.1 Diastereoselective Synthesis of 2-Deoxy-2-amino-5a-carba-β-l-mannopyranuronic Acid and 2-Deoxy-2-amino-5a-carba-β-l-mannopyranose

Efficient, total syntheses of novel 2-deoxy-2-amino-5a-carba-beta-L-mannopyranuronic acid (1) and 2-deoxy-2-amino-5a-carba-beta-L-mannopyranose (2), a positional stereoisomer of validamine, have been achieved in 28% and 24% overall yields and in 12 steps and 13 steps, respectively, from 2-[(tert-butyldimethylsilyl)oxy]furan (3) and (2S)-2,3-O-isopropylideneglyceraldehyde N-benzyl imine (4) via two highly diastereoselective Mukaiyama aldol-related chemical maneuvers. The strategy, which furnishes the targeted carbasugars in enantiopure forms, allows for complete control of the configuration at all five contiguous stereocenters of the targets by utilizing the sole element of chirality present in the aldimine progenitor 4.

Variable strategy toward carbasugars and relatives. 5.(1) Focus on preparation of chiral nonracemic medium-sized carbocycles

The feasibility of sequential vinylogous aldol (intermolecular)/silylative aldol (intramolecular) addition reactions involving furan- and pyrrole-based dienoxysilanes, 6 and 12, in the synthesis of carbasugar frameworks is illustrated by the preparation of the scantily investigated carbaseptanose and carbaoctanose representatives of this class of compounds. The target compounds, 1, 2, 3, ent-2, ent-3, and 4, were obtained from readily available carbohydrate precursors (5 and 19) in yields of 21-30% over 8-12 steps. The irreversible silylative ring-closing aldolisation of gamma-substituted dihydro-5H-furan-2-one and pyrrolidin-2-one aldehydes (9, 16, ent-16, and 22) driven by the TBSOTf/Pr(i)(2)EtN Lewis acid-Lewis base couple was shown to be a practical, diastereoselective maneuver to forge the densely functionalized, medium-sized core carbocycles.

Variable strategy toward carbasugars and relatives. 4. Viable access to (4a-carbapentofuranosyl)amines, (5a-carbahexopyranosyl)amines, and amino acids thereof

A chiral, divergent synthesis of two carbafuranosylamines, 1 and 2, two carbapyranosylamines, 3 and 4, two carbafuranosylamino acids, 5 and 6, and two carbapyranosylamino acids, 7 and 8, has been achieved. Highlights of the procedure include the following: a diastereoselective crossed vinylogous Mukaiyama aldol coupling between N-(tert-butoxycarbonyl)-2-[(tert-butyldimethylsilyl)oxy]pyrrole (TBSOP, 9) and 2,3-O-isopropylidene-D-glyceraldehyde (10) for the assembly of the target compound carbon backbone; a high-yielding silylative cycloaldolization that gives the cyclopentanoid and cyclohexanoid motifs; and a reductive or hydrolytic breakage of the lactam C(O)-N link to liberate the carbasugar and install the desired pseudo-anomeric amine and the hydroxymethyl or carboxyl functionalities. The sequences leading to trans-configured carbafuranosyl compounds 1 and 5 and carbapyranosyl compounds 3 and 7 were 12- and 13-step processes, with overall yields of 34%, 35%, 17%, and 16%. Cis-configured isomers 2, 4, 6, and 8 were obtained only in minor yields.