Takeshi Nishii

A total synthesis of (−)-antimycin A3b

Abstract (−)-Antimycin A 3b , the antipode of natural antibiotic antimycin A 3b , was synthesized utilizing the asymmetric aza-Claisen rearrangement.

Viridaphin A1 Glucoside, a Green Pigment Possessing Cytotoxic and Antibacterial Activity from the Aphid Megoura crassicauda

A green pigment, viridaphin A₁ glucoside (1), was isolated from the green aphid Megoura crassicauda. One- and two-dimensional NMR spectrometric analyses of 1 and its aglycone established the structure as an octacyclic compound. Viridaphin A₁ glucoside exhibited cytotoxicity against HL-60 human tumor cells with an IC₅₀ of 23 μM and antibacterial activity against Bacillus subtilis NBRC 3134 with a minimum inhibitory concentration of 10.0 μg/mL. These results suggested that aphid pigments may protect aphids from invasive species, including viruses and bacteria.

Megouraphin Glucosides: Two Yellowish Pigments from the Aphid Megoura crassicauda

Two new yellow pigments, megouraphin glucosides A (1) and B (2), were isolated from the aphid Megoura crassicauda. Their structures were established by detailed analysis of their 1D and 2D NMR spectra and via chemical conversion. INTRODUCTION Aphids produce novel pigments, such as the protoaphins, 1-7 furanaphin, 8 and the uroleuconaphines, 9,10 viridaphin A1 glucoside, 11 which may possess interesting biological activities such as cytotoxicity. 8,9,11,12 The presence of pigments is also important for expressing aphid body color, and it is presumed that subtle differences body coloration (color polymorphism) affect predator-prey interactions. 13 Therefore, the unique structures and potentially important biological activities of aphid pigments are of interest. As the first step, we have been studying the chemical structures of pigments in aphids. 8-11 In the present manuscript, we describe our studies of the aphid Megoura crassicauda (Figure 1) 14 and the isolation of two fluorescent yellow pigments named megouraphin glucosides A (1) and B (2) (Figure 2). Their chemical structures are described in detail. Figure 1. Megoura crassicauda HETEROCYCLES, Vol. 85, No. 1, 2012 95