Chemoenzymatic Synthesis of (−)-Ribisins A and B from Dibenzo[b,d]furan

Abstract

cis-Dihydrodiols, derived from monocyclic aromatic compounds, are valuable chiral pool intermediates for the synthesis of cyclic natural products. A drawback of this approach to the synthesis of polycyclic secondary metabolites, is that the additional rings must be annulated. To date, relatively few chiral natural products have been synthesized from polycyclic arene cis-dihydrodiols. Fungal metabolites ribisins A and B, have now be obtained by functional group manipulation of a major tricyclic arene metabolite, obtained from toluene dioxygenase-catalyzed regioselective and stereoselective cis-dihydroxylation of dibenzo[b,d]furan. The synthetic sequences were marginally shorter than the alternative routes using monocyclic arene cis-dihydrodiols and required no carbon-carbon bond-forming reaction.

Relations between work and entropy production for general information-driven, finite-state engines

“…. This expression is different from the general upper bound of [6], [7], [8], where it was argued that W N /NkT is asymptotically upper bounded by…”

“…As in the previous articles on models of physical systems with an information reservoir, our system consists of the following ingredients: a heat bath at temperature T , a work reservoir, here designated by a wheel loaded by a mass m, an information reservoir in the form of a digital input tape, a corresponding output tape, and a certain device, which is the demon, or ratchet, in the terminology of [6], [7], [8]. The ratchet interacts (separately) with each one of the other parts of the system (see Fig.…”

“…Several additional thought-provoking gedanken experiments have ultimately formed the basis for a vast amount of theoretical work associated with the role of informational ingredients in thermodynamics. An incomplete list of modern articles along these lines, include [1], [2], [3], [4], [5], [6], [7], [8], [9], [11], [12], [13], [14], [15], [16], [17], [18], [21], [22], [23], [24], [25], and [26]. These articles can be basically divided into two main categories.…”

“…In a recent series of interesting papers, [6], [7], [8], Boyd, Mandal and Crutchfield considered a system model of a demon (ratchet) that is implemented by a general finitestate machine (FSM) that simultaneously interacts with a heat reservoir (heat bath at fixed temperature), a work reservoir (i.e., a given mass that may be lifted by the machine), and an information reservoir (a digital tape, as described above). The state variable of the FSM, which manifests the memory of the ratchet to past input and output information, interacts with the current bit of the information reservoir during one unit of time, a.k.a.…”

“…The operation of the ratchet during one cycle is then characterized by the joint probability distribution of the next state and the output bit given the current state and the input bit. Perhaps the most important result in [6], [7] and [8], is that for a stationary input process (i.e., the incoming sequence of tape bits), the work extraction per cycle is asymptotically upper bounded by kT times the difference between the Shannon entropy rate of the tape output process and that of the input process (both in units of nats ‡ per cycle), i.e., eq. (5) of [6] (here k is the Boltzmann constant and T is the temperature).…”