Effect of the focal shaping generated from different double-mode cylindrical vector beams.

We investigate three-dimensional focus shaping generated from double-mode cylindrical vector beams with the Gaussian and Bessel-Gaussian pupil apodization functions by choosing the suitable polarization states of beams. Further, we compare them with that generated from the Laguerre-Gaussian pupil apodization function in the same situation. We find that the focus shaping generated from the Gaussian beam has the smallest zero intensity spot size.

Sharper focal spot generated by 4π tight focusing of higher-order Laguerre-Gaussian radially polarized beam.

The focal electric fields for a 4π high numerical aperture (NA) focusing system with both the doughnut and higher-order Laguerre-Gaussian (LG) radially polarized (RP) beams are investigated in the case of NA=1, and the full width at half-maximum values of the focal spots are calculated. Compared with the single-lens high NA focusing configuration, a sharper spot, whose size is reduced efficiently in the transverse as well as the axial direction, can be formed. Such size reduction is attributed to not only the destruction interference of the longitudinal component caused by the π phase shift between any two adjacent rings of the incident higher-order LG RP beam coming from one particular direction but also the perfect destruction interference of the radial component formed by the two counter-propagating incident beams.

Enantioselective syntheses of rigidiusculamides A and B: revision of the relative stereochemistry of rigidiusculamide A.

The first enantioselective synthesis of cytotoxic natural products rigidiusculamides A (ent-21) and B (8) has been achieved by two synthetic routes. The first one is convergent based on the common intermediate 11, obtained through a high yielding SmI(2) -mediated Reformatsky-type reaction. A highly diastereoselective one-pot Dess-Martin periodinane-mediated bis-oxidation allowed the direct conversion of the diastereomeric mixture of 11 into rigidiusculamide B (8).