Actin Filament in the First Cell Cycle Contributes to the Determination of the Anteroposterior Axis in Ascidian Development.

In many animal species, the body axis is determined by the relocalization of maternal determinants, organelles, or unique cell populations in a cytoskeleton-dependent manner. In the ascidian first cell cycle, the myoplasm, including mitochondria, endoplasmic reticulum (ER), and maternal mRNAs, move to the future posterior side concomitantly (called ooplasmic segregation or cytoplasmic and cortical reorganization). This translocation consists of first and second phases depending on the actin and microtubule, respectively.

Non-centrosomal microtubule structures regulated by egg activation signaling contribute to cytoplasmic and cortical reorganization in the ascidian egg.

In the first ascidian cell cycle, cytoplasmic and cortical reorganization is required for distributing maternal factors to their appropriate positions, resulting in the formation of the embryonic axis. This cytoplasmic reorganization is considered to depend on the cortical microfilament network in the first phase and on the sperm astral microtubule (MT) in the second phase. Recently, we described three novel MT structures: a deeply extended MT meshwork (DEM) in the entire subcortical region of the unfertilized egg, transiently accumulated MT fragments (TAF) in the vegetal pole, and a cortical MT array in the posterior vegetal cortex (CAMP).

Enantioselective synthesis of planar-chiral 1,n-dioxa[n]paracyclophanes via catalytic asymmetric ortho-lithiation.

Highly enantioselective ortho-lithiation and dilithiation of 1,n-dioxa[n]paracyclophanes were realized with the use of sec-butyllithium and a catalytic or stoichiometric amount of sparteine. Quenching with various electrophiles, such as iodine, iodomethane, and chlorodiphenylphosphine, afforded chiral mono- and disubstituted paracyclophanes with good to excellent ee.

The first asymmetric Sonogashira coupling for the enantioselective generation of planar chirality in paracyclophanes.

The double Sonogashira coupling of diiodoparacyclophanes with alkynes proceeded to give planarly chiral dialkynylparacyclophanes; a chiral Pd catalyst, which was prepared in situ from PdCl(2)(CH(3)CN)(2) and Taniaphos, realized the first asymmetric Sonogashira coupling with up to ca. 80% ee.

Enantioselective intramolecular [2 + 2 + 2] cycloaddition of enediynes for the synthesis of chiral cyclohexa-1,3-dienes.

The enantioselective intramolecular [2 + 2 + 2] cycloaddition of various enediynes, where two acetylenic moieties are connected by a trans-olefinic moiety, gave chiral tricyclic cyclohexa-1,3-dienes using Rh-H8-BINAP catalyst. In the case of carbon-atom-tethered enediynes, enantioselectivity was generally good-to-high regardless of the substituents on their alkyne termini. In contrast, with heteroatom-tethered enediynes, appropriate substituents were required to induce the oxidative coupling of alkyne and alkene moieties before that of two alkyne moieties, which would be important for highly enantioselective intramolecular cycloaddition.