162 Maheen et al.
the formation of zeolites and clays is the most spe-
cific link between impact cratering and the origin
of life [9]. Recently discovered world’s oldest rocks,
which resemble volcanic rocks, are rich in min-
erals such as garnet, quartz, and many other sili-
cates [14]. Similarly, hematite is ubiquitous both in
highly acidic hydrothermal vents [8] and in highly
acidic rivers, along with quartz [15,16]. Perlite, a hy-
drated volcanic glass, is formed in acidic volcanic
systems. The spatial mineralogical zonation of Al-
ternation Halos beneath Australian volcanic hosted
massive sulfide deposits is rich in perlite, quartz,
hematite, and many other silicates [17]. Hence, it
can be assumed that acidic hydrothermal environ-
ments would have played a significant role, not only
in the origin of life but also in the accumulation
of the necessary minerals and clays that had cat-
alytic properties to synthesize biomolecules. As dis-
cussed previously, there is a strong possibility of the
origin of life under hydrothermal conditions with
the aid of various prebiotic minerals as catalysts.
However, there still remains a problem that needs
to be resolved: the biological C O P bond forma-
tion under hydrothermal conditions. It is necessary
to find out the possible sources of phosphorus (P)
for the prebiotic synthesis under hydrothermal con-
ditions, the ultimate incorporation of P into organic
biomolecules, leading to the formation of C O P
type biological compounds under hydrothermal con-
ditions. The only known example of phosphorylation
reaction under simulated hydrothermal conditions
does not demonstrate the very incorporation of P
into the organic systems [18]. Biomolecules need
C O P and C P linkages, which are formed from
inorganic P by utilizing enzymes [19]. To the best
of our knowledge, hydrothermally induced C O P
bond formation has not been demonstrated yet. Or-
thophosphate is the most common source of P-type
compounds and it exists in the form of minerals
demonstrated earlier, which, so far, is the only re-
markable prebiotic synthesis of glycerol phosphates
[25]. In addition, there are no efficient methods de-
scribed to synthesize the phosphate esters under
prebiotic conditions [26]. Under ordinary organic
conditions, sn-glycerol-3-phosphate has been syn-
thesized [27–29], but these kinds of reactions are
very intricate. Here, for the first time, we report the
prebiotic hydrothermal synthesis of phosphate es-
ters including glycerol phosphates (Scheme 1) and
phosphoethanolamine (Scheme 2). Our work is one
of the most initial works to demonstrate the incor-
poration of P into the biological world hydrother-
mally and it also suggests how biological phosphates
would have synthesized for the hyperthermophiles
such as acidophiles. Moreover, it also throws some
light on the synthesis of biological phosphate esters
in the acidic hydrothermal systems.
RESULTS
The glycerol phosphates were detected and identi-
fied by comparing the retention time and MS (mass
spectrometric) fragments with those of standard.
The isomer of sn-glycerol-3-phosphate (glycerol-2-
phosphate) was identified by its same molecular
weight and retention time that showed a slight
difference with that of the standard sn-glycerol-
3-phosphate, whereas phosphoethanolamine was
characterized by peaks at 140, 79, and 97 (negative-
ion mode of MS). Its best yield was 0.83%, and it
could be obtained within a temperature range of
◦
100 to 120 C. We obtained glycerol-2-phosphate at
◦
100 C in both ways (with and without minerals).
However, the presence of minerals did increase the
yield (Table 2). Only perlite-catalyzed reaction at
◦
180 C could catalyze the formation of sn-glycerol-
3-phosphate. The yield of this reaction was 0.99%.
We then repeated the experiment without the min-
eral, but we were unsuccessful; rather, we obtained
glycerol-2-phosphate. This means that perlite was es-
sential for the synthesis of sn-glycerol-3-phosphate.
In our synthesis, the two isomers could not be ob-
tained simultaneously in the same reaction.
[
19,20]. These orthophosphate minerals are consid-
ered to be the major carriers of P on the earth
19]. There are many known sources of PO (phos-
[
4
phate) compounds [21]; however, it is believed that
the most reliable sources are the volcanic activities,
which can produce water-soluble polyphosphates
In our experiments, we also verified the effects of
temperature and pressure on the yields of our prod-
ucts. We selected glycerol phosphates as models to
find out the effects of aforementioned factors. It was
found that temperature greatly affects the yields of
glycerol phosphates. The effect of temperature on
the yields of glycerol phosphates is shown in Fig. 1.
via partial hydrolysis of P O10 [22,23]. Although, or-
4
thophosphate shows quite sluggish reactivity toward
biomolecules but still it could be considered as one
of the most acceptable source for phosphorylation
for the early developing life in the oceans, owing to
its easy availability [24].
Biological phosphate esters such as glycerol
phosphates and phosphoethanolamine enjoy a spe-
cial place in the biochemistry of living organisms.
Prebiotic synthesis of glycerol phosphates has been
◦
The maximum yields were obtained at 160 C. We
also studied the effects of pressure on our synthesis.
We conducted a series of experiments with a wide
range of pressure from 1 to 1.8 MPa and found that
Heteroatom Chemistry DOI 10.1002/hc