In our quest for antitumor activity in marine organisms occurring in Okinawan waters, we discovered a sponge which gave an extract inhibiting the growth of P388 mouse leukemia cells. Subsequent purification afforded a compound having an IC50 of 0.07 μg/mL, which proved to be a novel alkaloid. We now describe the isolation of manzamine A hydrochloride (1) and the determination of its absolute configuration by X-ray. The structure of manzamine A hydrochloride is unprecedented in nature. Moreover, its provenance is problematical as there appears to be no obvious biogenetic path. There has been great interest in the enantioselective aldol reactions of enolates with aldehydes to produce optically active β-hydroxycarbonyl compounds and considerable efforts have been devoted to developing effective chiral enolates, e.g., boron enolates of chiral ketones and imides and tin enolates coordinated with chiral diamines. Yet, there have been few reports on the use of chiral catalysts for such reactions. Here we report that a chiral ferrocenylphosphine-gold(1) complex catalyzes the asymmetric aldol reaction of an isocyanoacetate with aldehydes, producing optically active 5-alkyl-2-oxazoline-4-carboxylates with high enantio- and diastereoselectivity which are useful synthetic intermediates to optically active β-hydroxyamino acids and their derivatives.