Phosphine-Catalyzed Diastereoselective Synthesis of ß-Lactones from Disubstituted Ketenes and α-Chiral Oxyaldehydes.

In this article we describe a catalytic procedure for the diastereoselective synthesis of ß-lactones bearing two stereogenic centers, from disubstituted ketenes and α-chiral oxyaldehydes. Tri-n-butylphosphine was found to be the optimal catalyst in terms of effecting both good yield and diastereoselectivity (dr from 3:1 to 32:1 for 8 examples) in ß-lactone formation. The major isomer of the ß-lactone products was determined to be the anti-diastereomer, and its formation was rationalized by a polar Felkin-Anh model. Involvement of phosphonium enolate intermediates in the reaction mechanism was indicated through reaction monitoring by (31)P NMR spectroscopy. The utility of the methodology is demonstrated by a short synthesis of a (+)-peloruside A synthon.

Road traffic injuries in saudi arabia, and its impact on the working population.

UNLABELLED: This study aimed at describing the problem of Road Traffic Injuries (RTIs) in Saudi Arabia and it impact on the working population in terms of lost productivity. Registry review for Data on road traffic injuries and deaths were collected for the period of 1997 to 2002, and compared to population census during the same period. Potential Productive Years of Life Lost (PPYLL) was calculated. The total number of deaths due to RTIs was 21905 deaths and the total PPYLL due to RTIs was 459820.81. In all age groups, the losses in males were 1.91 to 8.52 times greater than in females, these differences were statistically significant. Males showed an increasing trend of PPYLL for 20 - 29, 10 - 19, 40 - 49 and 30 - 39 years age groups as ordered in descending order and increasing trend of PPYLL for 20 - 29 and 30 - 39 years age groups in females as ordered in descending order. The increasing trend was more expressive in males. PPYLL average was 76636.8 years annually in the productive years of life on years 1997 to 2002, with about 26.46% increase in 2002. CONCLUSION: RTIs is a major health problem affecting all age groups, working population are more vulnerable due to commuting. Losses in productive years are more prominent and serious in productive age groups.